Traditional Birthstone Calendar Month Genuine Cabochon

Transcription

Traditional Birthstone Calendar
Month
January
February
March
April
May
June
July
August
September
October
November
December
Genuine Cabochon Stone Genuine Faceted Stone
Garnet
Garnet
Amethyst
Amethyst
Bloodstone
Aquamarine
Pearl or Mother-of-Pearl
Diamond
Green Onyx
Emerald
Moonstone
Alexandrite or Pearl
Jasper
Ruby
Carnelian
Peridot
Lapis Lazuli
Blue Sapphire
Opal
Tourmaline (pink)
Citrine
Citrine or Topaz (golden)
Turquoise
Zircon or Tourmaline (blue)
Gemstones of the Zodiac
Sign
Aquarius
Pisces
Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpio
Sagittarius
Capricorn
Dates
January 21–February 21
February 22–March 21
March 22–April 20
April 21–May 21
May 22–June 21
June 22–July 22
July 23–August 22
August 23–September 22
September 23–October 23
October 24–November 21
November 22–December 21
December 22–January 20
Stone List
Amethyst
General
Stone
Garnet
Amethyst
Bloodstone
Sapphire
Agate
Emerald
Onyx
Carnelian
Peridot
Beryl
Topaz
Ruby
Category
Mineral variety
Chemical
formula
Silica (silicon dioxide, SiO2)
Identification
Color
Purple, violet
Crystal habit
6-sided prism ending in 6sided pyramid (typical)
Crystal system rhombohedral class 32
Specific gravity
2.65 constant; variable in
impure varieties
Twinning
Dauphine law, Brazil law, and Optical properties Uniaxial (+)
Japan law
Cleavage
None
Refractive index
nω = 1.543–1.553 nε =
1.552–1.554
Fracture
Conchoidal
Birefringence
+0.009 (B-G interval)
Mohs
7–lower in impure varieties
scalehardness
Pleochroism
None
Luster
Vitreous/glossy
Melting point
1650±75 °C
Streak
White
Solubility
insoluble in common
solvents
Diaphaneity
Transparent to translucent
Other
Piezoelectric
characteristics
Color
The deep colors are the most valuable, particularly a rich purple with rose
flashes. The "Siberian" deep purple with red and blue flash commands the
highest prices. So-called green amethyst does not really count as amethyst,
which is by definition violet or purple.
Lighting
In artificial light amethyst does not display its best color. It looks best in daylight,
more precisely, particularly just after sunrise and before sunset, when the light is
soft and warm.
Clarity
A fine amethyst is transparent, which means, the light passes through the stone
unhindered. A translucent amethyst slightly weakens the passage of the light
through the stone. The best quality amethyst is "clean", free of visible inclusions
of any kind. As the amethyst is plentiful, there is little reason to buy stones with
visible inclusions.
Cut
Due to the variability of the color distribution in the crystals, amethyst is often cut
as brilliant round to maximize the color. Other cuts can be used when the color
is better distributed. Amethyst is available in a wide range of calibrated sizes and
shapes, including many fancy shapes.
Amethyst location and deposits
The most important deposits are in Brazil, namely the "Palmeira" amethysts
of Rio Grande do Sul and the "Maraba" amethysts of Para. Other deposits
are found in Bolivia, Canada, India, Madagascar, Mexico, Myanmar (Burma),
Namibia, Russia, Sri Lanka, United States (Arizona), Uruguay and Zambia
Common Amethyst treatments
Heat treatment of 878-1382 degrees F (470-750 degrees C) results in light
yellow, red-brown, green or colorless varieties
Amethyst is the birthstone for those who are born in February or for
the Zodiacsign of Pisces.
Alexandrite
A type of crysoberyl
ategory
Mineral
Chemical
Beryllium aluminium oxide,
formula
BeAl2O4
Identification
Color
Various shades of green and
yellow; brownish, reddish;
rarely, blue
Crystal habit
slender prisms and tabular
form, dimensions are thin in
one direction.
Crystal system Orthorhombic 2/m2/m2/m
Twinning
Contact and penetration twins
common, often repeated
forming rosette structures
Cleavage
[110] Distinct, [010] Imperfect
Fracture
Conchoidal to uneven
Mohs
scalehardness
8.5
Luster
Vitreous
Streak
White
Specific gravity 3.5 - 3.84
Refractive
index
Biaxial (+) nα=1.745 nβ=1.748
nγ=1.754
Pleochroism
Strong in alexandrite
Major varieties
Alexandrite
Color change; green to red
Cymophane
Chatoyant
The mineral or gemstone chrysoberyl, not to be confused with beryl, is
an aluminate ofberyllium with the formula BeAl2O4.[1] The name chrysoberyl
is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos,
meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl
and beryl are two completely different gemstones. Chrysoberyl is the thirdhardest frequently encountered natural gemstone and lies at 8.5 on the hardness
scale, between corundum (9) and topaz (8).[2]
An interesting feature of its crystals are the cyclic twins called trillings. These
twinned crystals have a hexagonal appearance, but are the result of a triplet of
twins with each "twin" oriented at 120o to its neighbors and taking up 120o of the
cyclic trilling. If only two of the three possible twin orientations are present, a "V"shaped twin results.
Alexandrite is one of the rarest of all colored gemstones and is famed for its
color change from green in daylight to red under incandescent light. Fine faceted
alexandrite over 1 carat is more valuable than sapphire, ruby oremerald.
Alexandrite is a strongly pleochroicgem that will exhibit emerald green, red and
orange-yellow colors and tend to change color in artificial light compared to
daylight. The color change from red to green is due to strong absorption of light
in the yellow and blue portions of the spectrum. Typically,alexandrite has an
emerald-green color in daylight but exhibits a raspberry-red color in incandescent
light.
According to a popular but probably apocryphal story, alexandrite was
discovered by the Finnish mineralogist Nils Gustaf Nordenskjold, (1792 -1866)
on the tsarevitch Alexander's sixteenth birthday on April 17, 1834 and named
alexandrite in honor of the future Tsar Alexander II of Russia. It is apparently
true that alexandrite was first identified (but not discovered) by Nordenskjold, but
likely some years earlier, around 1831. It was Count Lev Alekseevich Perovskii
(1792-1856) who named the gem alexandrite.
Alexandrite is very rare because
composition. While it is a form of
has an extra trace elemement in
iron and titatnium. It is the
chromium that gives it the
green hue in daylight.
exhbiting chatoyancy or the cat's
known, but very rare.
of its chemical
chrysoberyl, it
addition to
presence of
emeraldAlexandrite
eye effect is
The original source of alexandrite in the Ural mountains in Russia has been
worked out. An important alexandrite deposit was found in 1987 in Minas Gerais
in Brazil, and other deposits are found in Burma, Madagascar, Sri Lanka,
India(Andra Pradesh) and Tanzania.
Alexandrite is rarely found in larger sizes. The largest cut alexandrite weighs 66
carats and is in the Smithsonian Institution in Washington, D.C.
Almandite garnet
Category
Silicate mineral
Chemical formula
Fe2+3Al2Si3O12
Identification
Color
reddish orange to
red, slightly purplish
red to reddish purple
and usually dark in
tone
Cleavage
none
Fracture
conchoidal [1]
Mohs scalehardness
7 - 7.5
Luster
greasy to vitreous
Specific gravity
4.05 (+.25, -.12) [1]
Polish luster
vitreous to
subadamantine [1]
Optical properties
Single refractive,
and often anomalous
double refractive [1]
Refractive index
1.790 (+/- .030) [1]
Birefringence
none
Pleochroism
none
Dispersion
.024 [1]
Ultravioletfluorescence inert
Absorption spectra
usually at 504, 520,
and 573nm, may also
have faint lines at
423, 460, 610 and
680-690nm [1]
Introduction
Almandine Garnet, or almandite garnet belongs to the large and varied
mineral group of garnet. Garnet comes from the Latin word "granatus",
which means grain, because many garnet deposits are small grains of red
crystals in or on their host rock. The dark brownish or purplish red stone is
popular for its excellent hardness (7.5 on the Mohs scale) and its brilliance
due to its high refractive index.
Garnet is the January birthstone.
Almandine Garnet colors
The color is a pure, dark brownish or purplish red. Its deep red color is
due to the presence of iron.
Buying Almandine Garnet
Color
Pure, deep red is the most desirable color.
Lighting
Clarity
In general, almandine garnet is an eye clean gem. Almandine garnet
sometimes has asbestos fiber inclusions. These will produce four-ray,
rarely six-ray, star stones when properly cut. They are highly prized by
collectors because of their rarity.
Cut
Very large crystals exist, but because of their dark tone, only small to
medium sized gems are faceted. These are often cut slightly shallow, to
let light pass through. Star stones are cut en cabochon. Almadine garnet
is found in a full range of shapes, including round, oval, pear and trillion.
Almandine Garnet location and deposits
Almandine Garnets are found in Brazil, India, Madagascar, Sri Lanka
and the United States. Smaller deposits exist in Austria and the Czech
Republic. Almandine garnet star-stones are found in India and the United
States (Idaho).
Common Almandine Garnet treatments
Like most garnet the Almandine Garnet is not artificially enhanced in any
way
Amazonite
troduction
Amazonite is a gemstone variety of green microcline, a feldspar mineral.
It is named after the Amazon river in Brazil. Surprisingly, no deposits
of it have been found there. The name may refer to the variable green
shades of the rainforest along the big river that are reflected in the
gemstone. Amazonite, is usually cut encabochon, with a rounded and
convex polished surface. In fact a fine quality amazonite can be mistaken
for precious jade. Like jade, Amazonite is often carvedas well. Amazonite
does not undergo any kind of treatment. Its relative softness of 6-6.5 on
the Mohs scale makes Amazonite vulnerable to pressure and scratches
and requires some care. Amazonite, though not common, is still very
affordable.
Amazonite is said to calm one's emotions and soothe nerves, and
to enhance creativity and the ability to express oneself. Perhaps the
strongest recommendation of its metaphysical powers is that Amazonite is
said to make your married life happier.
Amazonite colors
Amazonite color varies from green, yellow-green to blue-green. The color
distribution is irregular. Some gemstones may also exhibit fine white
streaks.
Buying Amazonite
Amazonite is slightly soft, 6-6.5 on the (Mohs scale), sensitive to pressure
and be scratched by harder stones. It is advisable to store amazonite
stones in separate boxes.
Color
Amazonite of a saturated, evenly distributed green would be the best
choice when it comes to color.
Lighting
Amazonite exposes its beauty best in daylight, more precisely in the hours
after sunrise and before sunset, when the light is warm and soft.
Clarity
Amazonite is opaque to translucent and rarely transparent. Its luster is
vitreous.
Cut
Amazonite is usually cut en cabochon. The green stone, set in silver,
creates nice pieces of jewelry, be it bracelets, necklaces, rings, earrings,
or brooches and pendants. Ornamental objects can be carved as well.
Amazonite location and deposits
The most important deposits are found in Colorado (since 1876). Other
locations are in Brazil, India, Kenya, Madagascar, Namibia, Russia and
Zimbabwe.
Common Amazonite treatments
Amazonite is not enhanced.
Amazonite gemology
Species: Feldspar
Color: Green, blue-green
Chemical composition: KalSi3O8 potassium aluminum silicate
Crystal system: Triclinic, prismatic
Hardness: 6-6.5 (Mohs scale)
Specific gravity: 2.56 – 2.58
Enlarge
Click to
Refractive index: 1.522 – 1.530
Birefringence: -0.008
Color of streak: White,
Absorption spectrum: Not diagnostic
Fluorescence: Weak; olive-green
The Amazonite zodiac
The best recommendation of its metaphysical power states: Amazonite
makes your married life happier.The safest approach is to wear the
gemstone in skin contact to the troubled part of the body. Amazonite is
said to calm one's emotions and soothe nerves, and to enhance creativity
and the ability to express oneself. The deeper the color of the amazonite,
the more intense the effect is said to be.
Ametrine
Ametrine Sometimes amethyst and citrine colors are found in the same
crystal ofquartz. These bicolor yellow and purple quartz gemstones are called
ametrine.Ametrine is a very durable gemstone suited for a variety of jewelry
uses. Ametrine is most typically faceted in a rectangular shape with a 50/50
pairing of amethystand citrine, though more creative cuts are becoming popular.
Ametrine deposits are limited.
Ametrine colors
Ametrine comes in bands of yellow and purple. The colors only reach a medium
level of saturation and are never very vivid (except in synthetic ametrine).
Ametrine typically exhibits an abrupt color transition.
Color
The two colors don't offer choices, cut is all that counts.
Lighting
It looks best in daylight, more precisely, particularly just after sunrise and before
sunset, when the light is soft and warm.
Clarity
Ametrine, like most quartz, is typically quite clean with good luster.
Ametrine location and deposits
The Anahi Mine in Bolivia is the major world producer of ametrine. Other deposits
are found in Brazil (Rio Grande de Sul).
Ametrine gemology
Species: Quartz
Color: Bands of yellow and purple
Chemical composition: SiO2 silicon dioxide
Crystal system: (Trigonal) compact
Hardness: 7 (Mohs scale)
Specific gravity: 2.65
Refractive index: 1.54 - 1.55
Birefringence: +0.009
Color of streak: White
Absorption spectrum: Cannot be evaluated
Fluorescence: None
The Ametrine zodiac, myth & legend
Ametrine combines the powers of amethyst and citrine in one gem. Therefore
ametrine can be the birthstone for those who are born in February or for
theZodiac sign of Pisces.
Ametrine can be assigned to the planets Jupiter, Mercury, Neptune and Pluto.
Ametrine could be said to be of help for headaches, pancreas and backache.
Andalusite
Category
Silicate
mineral nesosilicate
Chemical formula
Al2SiO5
Crystal symmetry
2/m 2/m 2/m Dipyramidal
Unit cell
a = 7.7980 Å b = 7.9031
Å c = 5.5566 Å; Z = 4
Identification
Color
Pink, violet, yellow,
green, white, gray; in thin
section, colorless to pink
or green
Crystal habit
As euhedral crystals or
columnar aggregates
having nearly square
cross sections; fibrous
compact to massive
Crystal system
orthorhombic
Twinning
On {101}, rare
Cleavage
Good on {110}, poor on
{100}
Fracture
uneven to subconchoidal
Mohs scalehardness
6.5 - 7.5
Luster
Vitreous
Streak
White
Diaphaneity
Transparent to nearly
opaque with inclusions
Specific gravity
3.17 (+/- .04)
Optical properties
double refractive, biaxial
negative; chiastolite has
anomalous aggregate
reaction.[1]
Refractive index
nα = 1.629 - 1.640 nβ =
1.633 - 1.644 nγ = 1.638
- 1.650
Birefringence
δ = 0.009 - 0.010
Pleochroism
Weak
2V angle
71 - 86°
Dispersion
r < v strong
Ultravioletfluorescence non-fluorescent
References
[1][2][3][4]
Andalusite is named after Andalusia, the province of Spain where it was first
discovered. Andalusite is a strongly pleiochroic gem that shows different colors
when viewed from different directions. While it is a strikingly beautiful gem, it is
largely unknown by the gem buying public. With a hardness of 7.5 on the Mohs
scale, it is very suitable for all kinds of jewelry.
Andalusite location and deposits
Deposits are found in Australia, Brazil, Canada, Russia, Spain (Andalusia), Sri
Lanka and the United States.
Apatite
Category
Phosphate mineral group
Chemical
formula
Ca5(PO4)3(F,Cl,OH)
Identification
Color
Transparent to translucent,
usually green, less often
colorless, yellow, blue to
violet, pink, brown.[1]
Crystal habit
Tabular, prismatic crystals,
massive, compact or granular
Crystal system Hexagonal Dipyramidal (6/m)
[2]
Cleavage
[0001] Indistinct, [1010]
Indistinct[2]
Fracture
Conchoidal to uneven[1]
Mohs
scalehardness
5[1]
Luster
Vitreous[1] to subresinous
Streak
White
Diaphaneity
Transparent to translucent[2]
Specific gravity 3.16 - 3.22[2]
Polish luster
Vitreous[1]
Optical
properties
Double refractive, uniaxial
negative[1]
Refractive
index
1.634 - 1.638 (+.012, -.006)[1]
Birefringence
.002-.008[1]
Pleochroism
Blue stones - strong, blue
and yellow to colorless.
Other colors are weak to very
weak.[1]
Dispersion
.013[1]
Apatite is infrequently used as a gemstone. Transparent stones of clean color
have been faceted, and chatoyant specimens have been cabochon cut.[1]
Chatoyant stones are known ascat's-eye apatite,[1] transparent green stones
are known as asparagus stone,[1] and blue stones have been called moroxite.[4]
Crystals of rutile may have grown in the crystal of apatite so when in
the right light, the cut stone displays a cat's eye effect. Major sources for
gem apatite are[1] Brazil, Burma, and Mexico. Other sources include[1]
Canada, Czechoslovakia,Germany, India, Madagascar, Mozambique, Norway, S
outh Africa, Spain, Sri Lanka, and theUS. It is also used in other countries.
Apatite colors
The range of colors includes colorless, pink, yellow, green, blue and violet.
Color
A rare variety is a rich purple from Maine. Blue Brazilian stones are second
in demand. A light green variety of apatite carries the trade name "asparagus
stone". The recent availability of the neon blue-green variety from Madagascar
has resulted in more apatite jewelry. The color of the best specimens of this type
rivals the famed Paraiba tourmalines, but apatite lacks tourmaline's toughness
andhardness. As for any other gems, color saturation defines the value.
Clarity
Apatite is a transparent gemstone. Some of the blue and yellow apatite
showchatoyancy and can be cut as cat's eyes.
Apatite location and deposits
Apatites are found in Brazil, India, Kenya, Madagascar, Mexico, Myanmar
(Burma), Norway, Sri Lanka, South Africa and the United States.
Aquamarine
Category
Silicate mineral
Chemical formula
Be3Al2(SiO3)6
Crystal symmetry
(6/m 2/m 2/m)
- Dihexagonal
Dipyramidal
Unit cell
a = 9.21 Å, c = 9.19
Å; Z = 2
Identification
Molar mass
537.50
Color
Green, Blue, Yellow,
Colorless, Pink &
others.
Crystal habit
Massive to
well Crystalline
Crystal system
Hexagonal (6/m 2/m
2/m) Space Group: P
6/mсc
Cleavage
Imperfect on the
[0001]
Fracture
Conchoidal
Mohs scalehardness
7.5–8
Luster
Vitreous
Streak
White
Diaphaneity
Transparent to
opaque
Specific gravity
Average 2.76
Optical properties
Uniaxial (-)
Refractive index
nω = 1.564–1.595,
nε = 1.568–1.602
Birefringence
δ = 0.0040–0.0070
Ultravioletfluorescence None (some fracture
filling materials used
to improve emerald's
clarity do fluoresce,
but the stone itself
does not)
The name derives from the Latin expression for seawater.Aquamarine is a
member of the beryl family and is known for its delicate blue or blue green
coloring, which accounts for its name. Aquamarine is the birthstone for March.
Aquamarine is a popular stone with very good hardness and luster.
Aquamarine colors
Like seawater, aquamarine comes in blue and green blue color. The more
saturated the color, the higher the value, though almost all aquamarine has a
light tone.
Color
Aquamarine is colored by trace amounts of iron that find their way into the crystal
structure. A saturated blue is the most desired color.
Clarity
Aquamarines of the best quality are clear, transparent gems. Some gems can
carry inclusions of long, hollow rods, a trademark of the beryl family. Aligned
traces of foreign minerals, a rare feature, cause a cat's eye effect or star
effect (asterism) with six rays in a vivid sheen. Cat's eye aquamarine and star
aquamarine usually command premium prices.
Aquamarine location and deposits
The leading producer of aquamarine is Brazil, with many mines spread
throughout the country. Other deposits found in Australia, Myanmar (Burma),
China, India, Kenya, Madagascar, Mozambique, Namibia, Nigeria, Pakistan,
Zambia, Zimbabwe, as well as in several U.S. locations.
Common Aquamarine treatments
Most aquamarines have been heat treated to produce the popular blue-green
colors from less desirable yellow or pale stones. Lower quality stones are heated
to 725-850 degrees F (400-450 degrees C) in order to change the color in favor
of the desired, permanent aquamarine blue. Higher temperatures would result in
discoloration.
Aquamarine is the birthstone for those born in March.
Aquamarine is said to be of help for arthritis, eye inflammation, sore throat and
varicose veins
Aventurine
Most gemstone names are unambiguous, but Aventurine is an exception. The
name is used both foraventurine feldspar and aventurine quartz. The aventurine
feldspar is now commonly sold under the namesunstone, leaving the name
aventurine to be used mainly for the quartz variety.
The reason both these gems were labelled as aventurine is due to their
resemblance to a type of Italian glass known as aventurine or goldstone.
Category
Oxide mineral
Chemical formula
Silica (silicon dioxide,
SiO2)
Identification
Molar mass
60 g / mol
Color
Various
Crystal system
Trigonal
Cleavage
Absent
Fracture
Uneven, splintery,
conchoidal
Mohs
scalehardness
6-7
Luster
Waxy, vitreous, dull,
greasy, silky
Streak
White
Diaphaneity
Translucent
Specific gravity
2.59 - 2.61
The majority of green and blue-green aventurine originates in India (particularly
in the vicinity of Mysore and Madras) where it is employed by prolific artisans.
Creamy white, gray and orange material is found in Chile, Spain and Russia.
Most material is carved into beads and figurines with only the finer examples
fashioned into cabochons, later being set into jewellery.
Beryl
Category
Silicate mineral
Chemical formula Be3Al2(SiO3)6
Crystal symmetry (6/m 2/m 2/m) - Dihexagonal
Dipyramidal
Unit cell
a = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Molar mass
537.50
Color
Green, Blue, Yellow,
Colorless, Pink & others.
Crystal habit
Massive to well Crystalline
Crystal system
Hexagonal (6/m 2/m 2/m)
Space Group: P 6/mсc
Cleavage
Imperfect on the [0001]
Fracture
Conchoidal
Mohs
scalehardness
7.5–8
Luster
Vitreous
Streak
White
Diaphaneity
Transparent to opaque
Specific gravity
Average 2.76
Optical
properties
Uniaxial (-)
Refractive index
nω = 1.564–1.595,
nε = 1.568–1.602
Beryl, not well known to the general public, is one of the most important
gem minerals. Beryl is colorless in pure form. The many different impurities
give beryl its varied coloration. Without these splendid color varieties,
beryl would be a rather ordinary gemstone with only average fire and
brilliance. Emerald is the green andaquamarine is the blue variety of
beryl. The name beryl is used for the red and golden varieties. Goshenite,
Morganite, Red beryl, Golden beryl and heliodor
Beryl of various colors is found most commonly in granitic pegmatites, but
also occurs in micaschists in the Ural Mountains, and limestone in Colombia.
Beryl is often associated with tinand tungsten ore bodies. Beryl is found
in Europe in Norway, Austria, Germany, Sweden(especially morganite),
and Ireland, as well as Brazil, Colombia, Madagascar, Russia, India,
South Africa, the United States, and Zambia. U.S. beryl locations are
in California, Colorado,Connecticut, Idaho, Maine, New Hampshire, North
Carolina, South Dakota and Utah.
Carnelian
Category
Chalcedony variety
Chemical formula
SiO2)
Identification
Molar mass
60 g / mol
Color
Reddish-brown
Crystal system
Trigonal
Cleavage
Absent
Fracture
Uneven, splintery,
conchoidal
Mohs
scale hardness
6-7
Luster
Vitreous, dull, greasy,
silky
Streak
White
Diaphaneity
Translucent
Specific gravity
2.59 - 2.61
Carnelian is a brownish red to red-orange variety of chalcedony or
cryptocrystallinequartz. Its name is believed to come from a variety of cherry
known as kornel.
It also is one of the birthstones listed in the ancient Arabic, Hebrew and and
Roman tables and is a Zodiac birthstone for the sign of Virgo.
The most important carnelian deposits are found in Brazil, Uruguay, India and
Madagascar.
Chalcedony
Category
Oxide mineral
Chemical formula
SiO2)
Identification
Molar mass
60 g / mol
Color
Various
Crystal system
Trigonal
Cleavage
Absent
Fracture
Uneven, splintery,
conchoidal
Mohs
scalehardness
6-7
Luster
Waxy, vitreous, dull,
greasy, silky
Streak
White
Diaphaneity
Translucent
Specific gravity
2.59 - 2.61
Chalcedony Technically, chalcedony is any form of microcrystalline or
cryptocrystalline quartz, meaning any form of quartz whose crystals are too small
to be seen without high magnification. In common practice, only the translucent,
single color types are sold as "chalcedony", whereas the rest of this group is sold
under individual variety names, such as agate, carnelian, bloodstone, jasper or
onyx. Chalcedony is named after the ancient seaport of Chalcedon (Kardikoy,
Turkey).
Chalcedony location and deposits
Australia: Agate, chrysoprase, bloodstone
Brazil: Agate, chalcedony, bloodstone, chrysoprase
China: Agate, bloodstone
India: Agate, chalcedony, bloodstone, carnelian, chrysoprase
Kazakhstan: Chrysoprase
Madagascar: Agate, chalcedony, chrysoprase
Mexico: Agate
Mongolia: Agate
Namibia: Agate, blue chalcedony, chalcedony,
Russia: Chrysoprase
Sri Lanka: Chalcedony,
Uruguay: Agate, chalcedony,
South Africa: Chrysoprase
Tanzania: chrysoprase
Zimbabwe: Chalcedony, chrysoprase
USA: Agate (Montana and Wyoming), chalcedony (California), chrysocolla
chalcedony (Arizona), bloodstone, blue chalcedony (California, Nevada, Oregon)
Common Chalcedony treatments
Carnelian is regularly heated to darken the red tones. Banded agates are dyed to
revitalize the colors.
Chrome Diopside
Category
Magnesium
minerals, Calcium
minerals, Silicate minerals
Chemical
formula
MgCaSi2O6
Identification
Color
Green
Crystal habit
Short prismatic crystals
common, may be granular[1]
Crystal system
Monoclinic[2]
Twinning
Simple and multiple twins
common on {100} and {001}
[1]
Cleavage
Distinct/good on {110}[2]
Fracture
Irregular/uneven,
conchoidal[2]
Tenacity
Brittle[2]
Mohs
scalehardness
5½ - 6½[2]
Luster
Vitreous to dull[2]
Streak
white[2]
Density
3.278 g/cm3[2]
Refractive index nα= 1.663 - 1.699, nβ= 1.671
- 1.705, nγ= 1.693 - 1.728[2]
Birefringence
δ = 0.030[2]
Dispersion
Weak to distinct, r>v [2]
Gemstone quality diopside is found in two forms: the black star diopside and
the chrome diopside (which includes chromium giving it a rich green colour). At
5.5–6.5 on the Mohs scale, chrome diopside is relatively soft to scratch. Mohs
scale of hardness does not measure tensile strength or resistance to fracture.
Violane is a manganese rich variety of diopside, violet to light blue in colour.[7]
Diopside location and deposits
Diopside deposits are found in Austria, Finland, India, Madagascar, Myanmar,
South Africa, Sri Lanka and the United States. Chrome diopside has thus far
been found only in Russia. Violane is only found in Piedmont, Italy.
Chrysocolla
Category
Silicate mineral
Chemical
formula
(Cu,Al)2H2Si2O5(OH)4·nH2O
Identification
Color
Blue, blue-green, green
Crystal habit
Massive, nodular, botryoidal
Crystal system
Orthorhombic
Cleavage
none
Fracture
Brittle to sectile
Mohs
scalehardness
2.5 - 3.5
Luster
Vitreous to dull
Streak
white to a blue-green color
Diaphaneity
Translucent to opaque
Specific gravity
1.9 - 2.4
Optical
properties
Uniaxial (+)
Refractive index
nω = 1.460 nε = 1.570
The name comes from the Greek chrysos, "gold", and kolla, "glue", in allusion to
the name of the material used to solder gold, and was first used by Theophrastus
in 315 BCE.
Chrysocolla is one of the lesser known gemstones, but it is a fascinating
mineral. It is sometimes confused with turquoise due to its color and its greasy
vitreous luster.Chrysocolla is one of a small group of copper-bearing gems that
includes malachite, azurite, larimar, oregon sunstone and paraiba tourmaline, as
well as turquoise.
By composition, chrysocolla is a hydrous copper silicate, often with traces of
oxides of copper, iron and manganese. It is a fairly soft stone at 2-4 on the Mohs
scale, somewhat softer than turquoise. It is almost always opaque, and often
occurs in shades of blue and green that have similarities to turquoise.
Traditionally chrysocolla is said to alleviate fear, guilt, and nervous tension. It
is thought to crystallize feelings of spiritually centered love, acceptance and
tolerance toward others.
Chrysocolla deposits are found in Chile, Israel, Mexico, Peru, Russia, Nevada in
the USA and in the Congo in Africa.
Chrysoprase
Chrysoprase is considered the rarest and most valuable stone in
the chalcedony quartz group. That's quite a distinction considering
that the chalcedony species includes agate,chalcedony, onyx,
carnelian, bloodstone andjasper. But chrysoprase, it is fair to say, is also
the least known of all the chalcedony varieties.
The term chalcedony refers both to the bluish-white-gray variety in
particular and to all the cryptocrystalline quartzes in general. The
cryptocrystalline quartzes have microscopically small crystals and a
waxy or dull luster in their natural state. The familiar macrocrystalline
quartzes such as amethystand citrine have much larger crystals which are
recognizable with the naked eye, and have a vitreous luster.
The name chrysoprase comes from the Greek for "gold-leek", though the
name seems misapplied today since chrysoprase is typically an applegreen to deep green. Chrysoprase is colored by traces of nickel and is in
fact one of the few gemstones colored by nickel. Most green gemstones
are colored by iron (such asperidot), chromium (emerald, chrome
tourmaline, chrome diopside) or vanadium (tsavorite garnet).
The color of chrysoprase can be quite vivid and is reminiscent of fine jade.
The gemological references warn that the color can fade under prolonged
exposure to sunlight or when heated, though the color may recover under
moist storage.
Chrysoprase has a hardness of 6.5 to 7 on the Mohs scale, and a density
of 2.58-2.64. It has a refractive index of 1.530-1.540. It ranges from
translucent to opaque.
Chrysoprase has been used as a decorative stone since ancient
times. A favorite of Frederick the Great of Prussia, chrysoprase can be
seen decorating many buildings in Prague, including the Chapel of St
Wenceslas. Today chrysoprase is carved or fashioned incabochons or
beads. It is also popular for intaglios and cameos.
Like all forms of chalcedony, chrysoprase is durable enough for all kinds
of jewelry applications, including rings. Chrysoprase is not known to be
treated in any way, though dyed green agate is sometimes used as a
simulant.
Chrysoprase occurs in serpentine rocks and in weathered materials
of nickel ore deposits. The most famous historical deposits were in
Poland, but that mine has been worked out since the 14th century.
Current sources include Australia, Brazil, India, Madagascar,
Tanzania,Kazakhstan, Russia, Zimbabwe, South Africa, Tanzania and the
USA (California).
Citrine
is one of the most popular and affordable gemstones. Named after the
French word for lemon, "citron", most citrines are actually more of a
golden than lemon yellow. Citrine colors includes yellow to gold to orange
brown and red shades of transparent quartz. In ancient times, citrine was
carried as a protection against snake venom and evil thoughts. Today
citrine is known as the merchant's stone and is associated with success
and prosperity.
Natural citrines are mostly pale yellow to golden. Much of the citrine in the market
is heat-treated amethyst, which nearly always has a reddish tint.
Citrine location and deposits
The most important deposits of natural citrine are in Brazil. Other locations
include Argentina, Madagascar, Myanmar (Burma), Namibia Russia, Scotland
and Spain.
Common Citrine treatments
Natural citrine is untreated and will typically exhibit some color zoning. Many
of the citrine in the market have been produced by heat-treating amethyst. The
Chrysoprase Ca
heat-treated stones will usually exhibit a reddish tint.
Citrine gemology
Species: Quartz
Color: Light to dark yellow, gold-brown
Chemical composition: SiO, silicon dioxide
Crystal system: Hexagonal (trigonal), hexagonal prisms with pyramids
Birefringence: +0.009
Optical character:
Fluorescence: None
The Citrine zodiac, myth & legend
Citrine is often used as a birthstone of November along with topaz.
In Antiquity, as well as in the Middle Ages people believed that the cosmos is
reflected in gemstones. Citrine is assigned to planet Mercury. Citrine is said to be
of help for backache.
Diamond
Category
Native Minerals
Chemical
formula
C
Identification
Molar mass
12.01 g·mol-1
Color
Typically yellow, brown or
gray to colorless. Less often
blue, green, black, translucent
white, pink, violet, orange,
purple and red.
Crystal habit
Octahedral
Crystal system
Isometric-Hexoctahedral
(Cubic)
Cleavage
111 (perfect in four directions)
Fracture
Conchoidal (shell-like)
Mohs
scalehardness
10
In mineralogy, diamond (from the ancient Greek αδάμας –
adámas "unbreakable") is anallotrope of carbon, where the carbon atoms
are arranged in a variation of the face-centered cubic crystal structure called
a diamond lattice. Diamond is less stable than graphite, but the conversion
rate from diamond to graphite is negligible at ambient conditions. Diamond
is renowned as a material with superlative physical qualities, most of which
originate from the strong covalent bonding between its atoms. In particular,
diamond has the highest hardnessand thermal conductivity of any bulk material.
Those properties determine the major industrial application of diamond in cutting
and polishing tools.
Diamond has remarkable optical characteristics. Because of its extremely
rigid lattice, it can be contaminated by very few types of impurities, such
as boron and nitrogen. Combined with wide transparency, this results in the
clear, colorless appearance of most natural diamonds. Small amounts of defects
or impurities (about one per million of lattice atoms) color diamond blue (boron),
yellow (nitrogen), brown (lattice defects), green, purple, pink, orange or red.
Diamond also has relatively high optical dispersion, that is ability to disperse light
of different colors, which results in its characteristic luster. Excellent optical and
mechanical properties, combined with efficient marketing, make diamond the
most popular gemstone.
The name diamond is derived from the ancient
Greek αδάμας (adámas), "proper", "unalterable", "unbreakable, untamed",
from ἀ- (a-), "un-" +δαμάω (damáō), "I overpower, I tame".[3] Diamonds
are thought to have been first recognized and mined in India, where
significant alluvial deposits of the stone could be found many centuries ago along
the rivers Penner, Krishna and Godavari. Diamonds have been known in India for
at least 3,000 years but most likely 6,000 years.[4]
Approximately 130 million carats (26,000 kg (57,000 lb)) of diamonds are
mined annually, with a total value of nearly US$9 billion, and about 100,000 kg
(220,000 lb) are synthesized annually.[39]
Roughly 49% of diamonds originate from central and southern Africa, although
significant sources of the mineral have been discovered in Canada, India,
Russia, Brazil, and Australia.[40] They are mined from kimberlite and lamproite
volcanic pipes, which can bring diamond crystals, originating from deep within
the Earth where high pressures and temperatures enable them to form, to the
surface. The mining and distribution of natural diamonds are subjects of frequent
controversy such as concerns over the sale of blood diamonds or conflict
diamonds by African paramilitary groups.[41]The diamond supply chain is
controlled by a limited number of powerful businesses, and is also highly
concentrated in a small number of locations around the world. In the U.S.,
diamonds have been found in Arkansas, Colorado, and Montana.[48][49] In 2004,
the discovery of a microscopic diamond in the U.S. led to the January 2008 bulksampling of kimberlite pipes in a remote part of Montana.[49]
Today, most commercially viable diamond deposits are in Russia (mostly
in Sakha Republic, for example Mir pipe and Udachnaya pipe),Botswana,
Australia (Northern and Western Australia) and the Democratic Republic of
Congo.[50] In 2005, Russia produced almost one-fifth of the global diamond
output, reports the British Geological Survey. Australia boasts the richest
diamantiferous pipe, with production from theArgyle diamond mine reaching peak
levels of 42 metric tons per year in the 1990s.[48][51] There are also commercial
deposits being actively mined in the Northwest Territories of Canada and Brazil.
Emerald
is the most precious stone in the beryl group. The name emerald comes
from the Greek "smaragdos" via the Old French "esmeralde", and really just
means 'green gemstone.' The wonderful green color of emerald is unparalleled
in the gem world. It is not surprising then that emerald is classified as one of the
traditional four precious stones along with sapphire, ruby and diamond. Emerald
is thebirthstone for May and for commemorating the 20th and 35th wedding
anniversaries.
Emerald's precious green color is caused by trace amounts of chromium and
vanadium. Emerald, by definition, is a medium or darker green to blue
green beryl, in which the green color is derived from impurities of chromium,
vanadium, or a combination of both. The most popular and valuable color is a
slightly bluish green in a medium dark tone with strong to vivid saturation. The
term "Colombian" emerald is often been used to describe vivid, slightly bluish
green stones of medium, to medium dark color, no matter what their actual
geographic origin. Emeralds of lighter color are sometimes
called "Brazilian" emerald, even if they were mined in Africa.
Emerald mining is nearly exclusively from host rocks, where the emerald has
grown into small veins or on walls of cavities.
Colombia is the world center of mining emerald. The Muzo mine, northwest of
Bogotá, produces fine-quality stones of a deep green color. The Chivor mine,
northeast of Bogotá, is another important deposit, other locations promise
additional successful mining results.
Brazil has various deposits in Bahia, Goias and Minas Gerais. The stones are
lighter than the Colombian ones, mostly yellow-green and are often free of
inclusions. Brazil also supplies rare emerald cat's eyes and extremely rare
emeralds with a six-ray star.
South Africa deposits concentrate in the northern Transvaal. But only five
percent of the stones found in the Cobra and Somerset Mines are of good
quality. Most stones are light or muddy and only suitable for cabochon cuts.
Zimbabwe has several deposits of emerald; the most important is the
Sandawana mine in the south. The crystals are small, but of very good quality.
Russia has deposits in the Ural north of Sverdlovsk. Good qualities are rare;
most stones are light or muddy and only suitable for cabochons.
Further deposits are in Afghanistan, Australia (New South Wales, Western
Australia), Ghana, India, Madagascar, Malawi, Mozambique, Namibia, Nigeria,
Pakistan, Tanzania, Zambia and the United States (North Carolina).
Common Emerald treatments
Oiling is a common treatment of emerald. This term refers to the practice of
immersing emeralds in a colorless oil or resin. Often this is done using a vacuum
chamber to assist penetration. Non-standard treatments go beyond this to using
green colored oils and hardened, epoxy-like resins.
These treatments dramatically improve the appearance of the gems, but
necessitate special care in cleaning and setting. Steam cleaners, solvents and
ultrasonic can remove the oils, making inclusions that had barely been visible
stand out in sharp relief. That damage is temporary only, since emeralds can be
re-oiled.
Emerald gemology
Species: Beryl
Color: Emerald green, green, slightly yellowish green
Chemical composition: Al2Be3Si6O18, aluminum beryllium silicate
Crystal system: (Hexagonal), hexagonal prisms
Hardness: 7.5-8 (Mohs scale)
Specific gravity: 2.67 - 2.78
Emerald is the birthstone for those who are born in May. Emerald is the
gemstone for commemorating the 20th and 35th wedding anniversaries.
Fire opal
Category
Mineraloid
Chemical formula Hydrated silica. SiO2·nH2O
Identification
Color
White
Crystal habit
Irregular veins, in masses,
in nodules
Crystal system
Amorphous[1]
Cleavage
None[1]
Fracture
Conchoidal to uneven[1]
Mohs
scalehardness
5.5–6.5[1]
Fire opal is an unusual variety of opal from Mexico. You will find two main types
of fire opal. One is a translucent yellow, orange or red with no play of color. The
other is brownish and has a play of color somewhat similar to the better known
precious opal. Fire opals, like all opals, are delicate gemstones, sensitive to
stress. Thus they are best suited for earrings, brooches, and pendants and need
to be treated carefully
The colors range from yellow to orange to brown and red. The best stones
usually show a vivid burnt red-orange combination
Opals are delicate gemstones. Their most significant weakness has to do with
their water content. If an opal is allowed to dry, it will crack and fade. If you live
in a very dry climate, or keep them in a dehumidified room, some precautions
are necessary. Keeping them in a tight plastic bag, with a damp piece of cotton
or fabric will prevent dehydration. Because of their water content, opals are also
sensitive to sudden changes in temperature.
Being somewhat soft, they scratch easily. Realize that a large component of
ordinary dust is quartz at 7 on the (Mohs scale) of hardness. At 5.5 to 6 in
hardness, simply wiping the dust off an opal will gradually reduce its polish. The
solution is to clean your opals using a soft cloth.
The finest fire opals are found in Mexico. Other deposits are in Brazil,
Guatemala, the United States and Australia.
Fire opals is usually untreated.
It is reported to be able to solve depressions and to help its wearer find the true
and real love.
Opal is the birthstone for those who are born in October.
Garnet
Category
Mineral
Chemical
formula
Ca3Al2(SiO4)3
Identification
Color
light to dark green, light to
dark yellow to reddish brown,
occasionally translucent to
opaque pink. It is also but
rarely found in colorless
form [1]
Crystal system
cubic [1]
Cleavage
none
Fracture
conchoidal to uneven [1]
Mohs
scalehardness
7 to 7.5 [1]
Luster
greasy to vitreous [1]
Specific gravity 3.61 (+.12 -.04)
Polish luster
vitreous [1]
Optical
properties
Single refractive, often
anomalous double
refractive [1]
Refractive index 1.740 (+.12 -.04) [1]
Garnet is derived from the Latin word "granum" meaning "grain". This refers to
the typically rounded shape of Garnet and also reminiscent of the seeds of the
pomegranate. Garnets have been widely known for thousands of years. Even
Noah, it is reported, used a lantern from garnet in order to safely steer his Ark
through the darkness of the night. Although the color red occurs most frequently,
there are also garnets showing different shades of green, pale to bright yellow,
fiery orange and fine earth- and umbra-shades. Only blue is the color that is not
available in Garnet.
Garnet colors
Although the color red is occurs most frequently, there are also garnets showing
different shades of green, pale to bright yellow, fiery orange and fine earth- and
umbra-shades. Blue is the only color that is not available in Garnet. Color change
garnets are mostly pyrope and spessartite in composition.
The colorful members of the garnet group:
Pyrope, red garnet, frequently with brown tint
Rhodolite, purplish red or rose-color garnet
Almandite, red garnet with violet tint
Spessartite, orange to red-brown garnet. The best specimen comes from
Namibia and is called "Mandarin Spessartine".
Grossularite, colorless, green, yellow, brown garnet
Hydrogrossular, dense, opaque greenish variety of grossularite
Hessonite, brown-red variety of garnet
Leuco garnet, colorless variety of grossularite
Tsavorite, green to emerald green garnet
Andradite, black, brown, yellow-brown garnet
Demantoid, the most valuable garnet, green to emerald green
Melanite, opaque black variety of andradite
Tapazolite, yellow to lemon yellow, topaz-like variety of andradite
Uvarovite, emerald green garnet that rarely occurs in gemstone quality.
garnet location and deposits
Pyrope: China, Madagascar, Myanmar, South Africa, Sri Lanka, Tanzania, USA
Rhodolite: Brazil, India, Sri Lanka, Thailand, USA
Almandite: Brazil, India, Madagascar, Sri Lanka and the United States. Smaller
deposits exist in Austria and the Czech Republic. Almandine garnet star-stones
are found in India and the United States (Idaho).
Spessartite: Brazil, China, Kenya, Madagascar, Myanmar, Namibia, Sri
Lanka, Tanzania, USA. The best specimens come from Namibia and are
called "Mandarin Spessartine (Spessartite) "
Grossularite: Canada, Kenya, Mali, Pakistan, Russia, South Africa, Sri Lanka,
Tanzania, USA
Hydrogrossular: Myanmar, South Africa, Zambia
Hessonite: Brazil, Canada, Madagascar, Sri Lanka, Tanzania, USA
Leuco garnet: Canada, Mexico, Tanzania
Tsavorite: Kenya, Tanzania
Andradite: Russia
Demantoid: China, Korea, Russia, USA, Zaire
Melanite: France, Germany, Italy, USA
Tapazolite: Italy, Switzerland, USA
Uvarovite: Canada, Finland, India, Poland, Russia, USA
Garnet is the birthstone for those who are born in January. On the Zodiac chart, it
is listed as the stone for Aquarius.
Garnet is said to be of help for arthritis, pancreas, varicose veins and problems
with testicles and toenails.
Hematite
Category
Oxide mineral
Chemical formula
iron(III) oxide, Fe2O3, αFe2O3
Identification
Color
Metallic gray to earthy red
tones
Crystal habit
Tabular to thick crystals
Crystal system
Trigonal - hexagonal
scalenohedral
Cleavage
None
Fracture
Uneven to sub-conchoidal
Mohs
scalehardness
5.5 - 6.5
Luster
Metallic to splendent
Streak
Bright red to dark red
Specific gravity
4.9 - 5.3
Refractive index
Opaque
Hematite, an iron oxide, derives its name from the Greek word for blood, since it
is red when sliced thinly or powdered. Hematite crystallizes in the rhombohedral
crystal system, and has the same crystal structure assapphire and ruby.
Hematite is always opaque and is typically a blackish grey. You will find it cut as
cabochons or faceted, and engravings are particularly popular. Hematite was a
traditional material for signet rings. When highly polished it can sometimes look
like silver.
Good specimens of hematite come
from England, Mexico, Brazil, Australia, United States and Canada.
Please also check Pyrite
Idocrase Vesuvianite
Category
Mineral
Chemical
formula
Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)
2(OH,F)4
Identification
Molar mass
1,422.09 gm
Color
Yellow, green, brown - rarely
blue or red
Crystal habit
Massive to columnar
Crystal system Tetragonal
Cleavage
Poor to very poor
Fracture
Sub conchoidal
Mohs
6.5
scalehardness
Luster
Vitreous to resinous
Streak
White
Diaphaneity
Subtransparent to Translucent
Idocrase is a rare gemstone, usually found in shades of green but sometimes
in yellow-brown or pale blue. Idocrase belongs to the silicate group of minerals.
While the name idocrase is used for rare gemstone-quality specimens, the
mineral is usually known by the name vesuvianite, since the first samples were
found on the Mt. Vesuvius volcano.
Idocrase is not only rare, but transparent specimens that can be faceted count
as very rare indeed. Most gem-quality idocrase is opaque with an appearance
similar to jade. The opaque specimens have a greasy or resinous luster, while
the rare transparent form has a vitreous luster
Idocrase or vesuvianite is found in a number of locations in the world. They
include Quebec in Canada, Mt. Vesuvius in Italy, the Ural Mountains in Russia,
Switzerland, Kenya and Tanzania. But there are very few sources of gem-quality
crystals. Recent finds in Kenya and Tanzania have brought some very fine
stones to the market, albeit in limited quantity. One source of cabochon grade
material is California, USA. It has been marketed as Californite or California
Jade.
Topaz
Category
Silicate mineral
Chemical
Al2SiO4(F,OH)2
formula
Identification
Color
Clear (if no impurities), blue,
brown, orange, gray, yellow,
green, pink and reddish pink.
Crystal system
orthorhombic
Cleavage
[001] Perfect
Fracture
conchoidal
Mohs
scalehardness
8
Luster
glassy
Streak
white
Diaphaneity
Transparent
Specific gravity
3.49–3.57
Optical
properties
Biaxial (+)
Refractive index nα = 1.606–1.629
nβ = 1.609–1.631
nγ = 1.616–1.638
Topaz comes in many colors, including clear, brown, yellow, orange, red, pink
and blue. The blue topaz, with a pale to medium blue color created by irradiation,
can be found in very large sizes at affordable prices. The fine golden-yellow
variety, known as Imperial Topaz, is relatively scarce. Topaz colors are rarely
vivid. The most common color is yellow with a red tint; the most valuable is pink
to reddish. The coloring agents are iron and chromium.
The name topaz is most probably derived from an island in the Red
Sea, "Topazos", today called Zabargad, the ancient source of peridot. In former
times all golden-brown and sometimes also green gemstones were called
topaz, which caused sufficient confusion such that today real topaz is referred to
as precious topaz.
and blue. The blue topaz, with a pale to medium blue color created by irradiation,
to reddish; the most popular is blue. The coloring agents are iron and chromium.
Blue topaz: Natural blue topaz is rare. Found in all major deposits and also in
England (Cornwall), Northern Ireland and Scotland. Most of the blue topazes are
enhanced colorless topaz gemstone (see common treatment)
Champagne topaz: One of the very few naturally colored varieties of topaz in a
light to medium shade of brown, primarily found in Mexico.
Imperial topaz: The most sought after of all natural topaz. Its rich golden color
is generally not enhanced by any kind of treatment. The most important deposit
was found in Minas Gerais, Brazil.
Pink topaz: A natural pink topaz is very rare and costly. The vast majority of pink
topazes are heat-treated yellow stones that turn pink. The most valuable variety
of topaz can be found in Brazil, Pakistan and Russia.
Brazil (Minas Gerais) is the most important supplier for topaz. Other deposits
are in Afghanistan, Australia, China, Japan, Madagascar, Mexico, Myanmar,
Namibia, Nigeria, Pakistan, Russia, Sri Lanka, Ukraine, United States and
Zimbabwe. Natural light blue topaz is also found in England (Cornwall), Northern
Ireland and Scotland.
Blue topaz begins as colorless or very lightly tinted natural topaz crystals, which
are then irradiated to change the color to blue and heated to stabilize the change.
Neutron bombardment in a nuclear reactor produces the deep slightly greenish
or grayish "London Blue", while electron bombardment in a linear accelerator
results in the light aqua-like blue known as "Sky Blue". Combinations of both
treatments produce the highly saturated "Swiss" and "Electric" blues. If neutron
bombardment has been used, there is residual radioactivity, and the gems must
be held, up to a year, before they have "cooled" enough to be worn.
In general, blue topaz is modestly priced. Due to the expenses of reactor time the
London Blue color is short in supply and climbs in value.
In early 1998, a new type of enhanced topaz made its appearance, the surfaceenhanced topaz, with colors described as blue to greenish-blue or emerald
green.
The vast majority of pink topazes are heat-treated yellow stones that turn pink.
Topaz is the birthstone for those who are born in the month of November.
Iolite
Category
Silicate mineral
Chemical
formula
(Mg,Fe)2Al4Si5O18
Strunz
classification
09.CJ.10
Dana
classification
61.02.01.01 Cordierite group
Crystal
symmetry
2/m 2/m 2/m Orthorhombic Dipyramidal
Unit cell
a = 17.079 Å, b = 9.730 Å, c =
9.356 Å; Z = 4
Identification
Color
Blue, smoky blue, bluish
violet; greenish, yellowish
brown, gray; colorless to very
pale blue in thin section
Crystal habit
Pseudo-hexagonal prismatic
twins, as imbedded grains,
and massive
Crystal system
Orthorhombic - Dipyramidal
Space Group: C ccm
Twinning
Common on {110}, {130},
simple, lamellar, cyclical
Cleavage
Fair on {100}, poor on {001}
and {010}
Fracture
Subconchoidal
Tenacity
Brittle
Mohs
scalehardness
7 - 7.5
Luster
Greasy or vitreous
Streak
White
Optical
properties
Usually optically (-),
sometimes (+); 2V = 0-90°
Refractive index nα = 1.527 - 1.560 nβ = 1.532
- 1.574 nγ = 1.538 - 1.578
Indices increase with Fe
content.
Kunzite
Kunzite is the pale pink-violet to light violet species of the
mineral spodumene.Kunzite is named as a tribute to George F. Kunz, the
legendary American mineralogist and buyer for Tiffany & Co, who first described
the gem in 1902. Kunzite is the pink-violet sister to the yellow-green hiddenite,
another specimen of the spodumene family. Kunzite is strongly pleochroic,
meaning there is a color intensity variation when a crystal of it is viewed from
different directions. The top and bottom of the crystal reveal the deepest colors.
Kunzite is very difficult to cut to ensure that the light passes trough the gem and
accents the desired color. Kunzite is said to help one to understand and interact
better with others.
Kunzite is a transparent gem, but can show frequently aligned inclusions such as
tubes or fracture. An eye clean gem would be the best choice.
Species: Spodumene
Color: Pink-violet, light violet
Chemical composition: LiAlSi206 lithium aluminum silicate
Crystal system: Monoclinic, prismatic, tabular
Hardness: 6.5 - 7 (Mohs scale)
Birefringence: +0.014 to +0.016
Fluorescence: Strong: yellow-red, orange
The Kunzite zodiac, myth & legend
Some consider kunzite a modern-day birthstone for February, which lacks
support of the traditionalists. The wearer of a kunzite gemstone is believed to be
blessed with good fortune. Kunzite is said to help one to understand and interact
better with others.
reflected in gemstones. Kunzite is assigned to the planets Pluto and Venus.
Kyanite
Kyanite is named after the Greek word for "blue". Its color indeed can make it a
lovely gem with a near sapphire-like blue. Usually its color is blue but also can be
colorless, white, gray, green or yellow. Color is often not consistent throughout
the crystal, often showing white streaks in a medium blue. Luster is vitreous to
almost pearly. It's a nice gemstone for earrings or pendants. Kyanite is believed
to aid self-expression, communication and supernatural abilities.
The most desired color would be a sapphire-like blue. Colorless stones are quite
rare.
Kyanite location and deposits
Deposits are found in Austria, Brazil, India, Kenya, Myanmar, Serbia,
Switzerland, United States and Zimbabwe.
Kyanite gemology
Species: Kyanite
Color: Blue to colorless, blue-green, brown
Chemical composition: Al2SiO5 aluminum silicate
Crystal system: Triclinic, long, flat prisms
Hardness: Along axes 4 - 4.5, across 6-7 (Mohs scale)
Absorption spectrum: 706, 689, 671, 652, 446, 433
Fluorescence: Weak: red
In ancient times it was believed that a kyanite suspended from a human hair
could fallow the Earth's magnetic force like a compass needle. In those times
travelers took kyanite along with them, when they entered unknown territories.
Labradorite
Labradorite is an iridescent gemstone with a fascinating schiller or metallic luster
when viewed from certain angles. A member of the plagioclasefeldspar group
along with andesine and sunstone.
The ground color oflabradorite is a dark smoky gray, but when light strikes the
stone in a particular direction, it displays striking rainbow-colored reflections.
Most typically, these metallic tints are violet, blue and green; but sometimes
yellow, orange and red can be seen. This effect is so unique to labradorite that it
is referred to as labradorescence.
The labradorescent effect is believed to be due to the presence of very fine
platelets of different compositions as well as minute inclusions of limenite, rutile
and possible magnetite which cause the diffraction of light.
Labradorite was named after the Labrador Peninsula in eastern Canada where it
was first found around 1770. Deposits have also been found in Australia, Finland,
Madagascar, India, Mexico and the Adirondack Mountains in the United States.
labradorite is reasonably hard at 6 to 6.5 on theMohs scale
Lapis
Lapis Lazuli is used for more than 6000 years for jewelry and ornamental
objects. Its name is from "lapis," the Latin word for stone and "azul," the Arabian
word for blue. Lapis lazuli is made up of 25 to 40 percent lazurite, plus several
minerals (sodalite, hauyne, calcite, and pyrite) that influence color and its
distribution. Based on that varying composition, lapis lazuli is considered a rock,
not a mineral.
Lapis Lazuli defines its color by name, the blue stone. Its blue varies from lazur
blue, to violet and greenish-blue. Its coloring agent is sulfur. In the very best
quality stones the color is evenly distributed, but in general the color is spotted.
The composition of the minerals, other than lazurite, influences the color as well.
Well-distributed fine pyrite highlights the color with a brassy gold shimmer. Too
much of the same mineral causes a dull, greenish tint. Lapis Lazuli fans may not
agree as to how much pyrite is ideal. But most admirers and collectors of fine
lapis lazuli agree -- the less calcite, the better. Calcite can be seen as streaks or
patches within the darker blue, or it can predominate in the mix giving the rock an
overall lighter blue shade.
Lapis lazuli is opaque, with a vitreous and greasy luster.
The oldest deposits, discovered 6000 years ago, are located in the difficult
terrain of the West Hindu-Kush Mountains in Afghanistan. They still produce the
finest quality. Other deposits have been found in Angola, Canada, Chile (North
of Santiago), Myanmar, Pakistan, Russia (Lake Baikal) and the United States
(California and Colorado).
Lapis Lazuli gemology
Species: Lapis Lazuli
Color: Lazur-blue, violet, greenish-blue
Chemical composition: (Na,Ca)8(SiO4,S,CI)2I(AlSi)4l6 sodium calcium aluminum
silicate
Crystal system: Cubic (rare), dense aggregates
Hardness: 5-6 (Mohs scale)
Specific gravity: 2.50 – 3.00
Refractive index: About 1.50
Birefringence: None
Color of streak: Light blue
For people around the world, lapis lazuli is considered a stone of truth and
friendship. The blue stone is reputed to promote harmony in relationships.
In Antiquity, as well as in the Middle Ages, people believed that the cosmos was
reflected in gemstones. Lapis lazuli is assigned to the planet Jupiter. The esoteric
movement revived the ancient believe and the gem industry made it another
marketing tool to promote certain gems.
The healing powers of gems remain a controversial issue, but are mentioned
for centuries by healers, shamans and medicine men. Whether it’s a fact or a
placebo effect doesn’t matter, if it helps.
Lapis lazuli is said to be of help for headaches, sore throat and varicose veins.
Moonstone
Moonstone owes its name to the white, almost magical shimmer that resembles
moonshine. Blue-whitish light glides over the surface when the stone is cut
cabochon. Gemologists call this phenomena adularescence, which originates
from the interior structure of the gemstone in scales or lamellas. Incoming rays of
light are refracted inside the stone and scattered, creating a unique play of light,
which makes Moonstone so special and coveted.Moonstone is the most well
known potassium feldspar of the orthoclasespecies
In Arab countries women often sew moonstone into their garments, because it's
considered a symbol of fertility.
Moonstone is the birthstone for those who are born in June.
Moonstone from Sri Lanka, the classical country of origin for Moonstone,
shimmers pale blue on an almost transparent ground. Specimens from India
show cloudlike plays of light and shade on beige brown, green, orange, or
simple brown background. They do come as well in blue and peach, smoke and
champagne colored, or in black and reddish.
Deposits are found in Brazil, India, Madagascar, Myanmar, Sri Lanka and the
United States.
Moonstone gemology
Species: Feldspar
Color: Colorless, yellow, pale sheen
Chemical composition: KalSi3O8 potassium aluminum silicate
Crystal system: Monoclinic, prismatic
Hardness: 6-6.5 (Mohs scale)
Fluorescence: Weak; bluish, orange
Onyx
It’s a type of Chelcedony so please refer to chalcedony.
Peridot
Peridot belongs to the forsterite-fayalite mineral series, which is part of the
olivine group. It is one of the "idiochromatic" gems, meaning its color comes from
the basic chemical composition of the mineral itself, not from minor impurities,
and therefore will only be found in shades of green. As a matter of fact peridot is
one of the few gemstones found in only one color.
The name peridot most probably derives from the Arabic word "faridat" for gem.
It's also called chrysolith (derived from the Greek word "goldstone") and olivine,
because of its color and membership to the olivine group.
Historically the volcanic island Zabargad (St. John) in the Red Sea, east of
Egypt, was the most important deposit that was exploited for 3500 years.
Today's main deposits are in Arizona, China, Vietnam and Pakistan. The
Pakistani peridot in particular is very fine, and a new find in Pakistan in the mid1990's has made peridot available to a wider market.
Historically the volcanic island Zabargad (St. John) in the Red Sea, east off
Egypt, was the most important deposit that was exploited for 3500 years,
abandoned for many centuries, rediscovered only around 1900 and has been
completely exploited since. The most important deposits nowadays are found
in Pakistan (Kashmir region and Pakistan-Afghanistan border region) and
is regarded as being of the finest quality. Beautiful material is also found in
upper Myanmar and Vietnam. Other deposits have been found in Australia
(Queensland), Brazil (Minas Gerais), China, Kenya, Mexico, Norway (north of
Bergen), South Africa, Sri Lanka, Tanzania and the United States (Arizona and
Hawaii).
Peridot gemology
Species: olivine
Color: Yellow-green, olive-green, brownish
Chemical composition: (Mg,Fe)2SiO4 magnesium iron silicate
Crystal system: Orthorhombic; short compact prisms, vertically striated
n ancient believes peridot was a gift of Mother Nature to celebrate the annual
creation of a new world. National leaders who publicly wore peridot were in
former times thought to be gentle, fair and wise.
In Antiquity, as well as in the Middle Ages people believed that the cosmos
is reflected in gemstones. Peridot is assigned to planet Saturn. The esoteric
movement revived the ancient belief and the gem industry made it another
marketing tool to promote certain gems.
Prehnite
Hundreds of minerals have been named after individuals, including a number of
gemstones. The gemstones include Hiddenite (W.E. Hidden), Kunzite(George
Frederic Kunz), Morganite (J.P. Morgan) andZoisite (Sigmund Zois).
But there is one gemstone that has the distinction of being the very first mineral
ever named after an individual. The gemstone Prehnite was named for its
discoverer, Colonel Hendrik von Prehn (1733-1785), a Dutch mineralogist and an
early governor of the Cape of Good Hope colony.Prehnite was also the very first
mineral to be named and described from South Africa, long before South Africa
became an important source for precious gems.
Prehnite is a hydrated calcium aluminum silicate that occurs in a soft yellowgreen to apple-green color. Many specimens have an intriguing luminous quality.
It has a vitreous to mother-of-pearl luster. Prehnite is a medium-hard gem with a
rating of 6 to 6.5 on the Mohs scale. Most prehnite is translucent but transparent
specimens are sometimes found. Prehnite has a density or specific gravity of
2.82-2.94 and a refractive index of 1.611-1.669.
Deposits are found in South Africa, Australia, China, Scotland and the United
States
Prehnite is said to encourages composure, forgiveness and acceptance and is
excellent for meditation. Some people also believe that prehnite helps sufferers
of claustrophobia.
Quartz
Quartz is one of the most common minerals on earth and is well known in the
gems world. Quartz is attractive and durable, as well as inexpensive. It can be
cut and carved in many forms and sizes. Quartz is named after a Slavic word
for "hard".
There are two main varieties of quartz, though they share the same chemical
composition, silicon dioxide. Macrocrystalline quartz, includes stones
likeamethyst, aventurine, rock crystal, blue quartz, citrine, hawk's eye, prasiolite,
quartz cat's eye, smoky quartz, rose quartz and tiger's eye. The quartz is
mostly transparent to translucent. Cryptocrystalline quartz, with microscopically
small crystals, is known as chalcedony, and includes agate, chrysoprase,
bloodstone, jasper and carnelian. Crytocrystalline quartz is usually opaque or
translucent.
The colors of macrocrystalline quartz are as follows:
Rock crystal: Colorless. Material that can be cut is rare. Inclusions are of
goethite, gold, pyrite, rutile or tourmaline. The luster is vitreous.
Smoky quartz: Brown to black, smoky gray. The coloring is caused by natural
and artificial gamma rays. Frequent inclusions are rutile needles.
Amethyst: Purple, violet, pale red-violet. Amethyst is the most highly valued
stone in the quartz group. The coloring agent is iron.
Amethyst Quartz: Violet with whitish stripes. Amethyst quartz is a more compact
formation of amethyst, layered and striped with milky quartz.
Ametrine: Yellow and violet. Color-zoned quartz variety that consists half of
amethyst and citrine.
Citrine: Light yellow to dark yellow, gold-brown. The coloring agent is iron. Many
commercial citrines are heat-treated amethyst. Natural citrines are mostly pale
yellow. If heat-treated they acquire a reddish tint.
Prasiolite: Leek-green. Prasiolite is not found in nature. Prasiolite is produced by
heat treatment of amethyst or yellowish quartz.
Rose quartz: Strong pink, pale pink. Coloring agent is titanium. Traces of
included rutile needles cause six-rayed stars when cut en cabochon. Larger clear
stones can be faceted. Rose quartz crystals tend to be cloudy, which deepens
the color. Transparent crystals are extremely rare.
Aventurine: Green, red-brown, gold-brown. Mostly dark green with metallic
glittery appearance caused by included fuchsite (green mica), or red- to goldbrown caused by hematite leaves.
Prase: Leek-green. Prase is a quartz aggregate, usually classified as a
chalcedony whose color agent are chlorite inclusions.
Blue quartz: Turbid blue. Inclusions of crocidolite fibers cause the color.
Quartz cat's eye: White, gray, green, yellow, brown (Cat's eye: Is a reflection of
light by parallel fibers, needles, or channels, which resembles the slit eye of a
cat. When the stone is rotated, the cat's eye glides over the surface.)
Hawk's eye: Blue-gray to blue green (Hawk's eye: Small ray of light on the
surface that is reminiscent of the eye of a bird of prey)
Tiger's eye: Gold-yellow, gold-brown (Similar to Hawk's eye effect, ray of light is
brown colored due to oxidized iron inclusions)
The colors of cryptocrystalline quartz:
In the narrow sense, chalcedony (species name for all cryptocrystalline quartzes)
will mean any translucent, cryptocrystalline quartz with a single color, whether it
has a special variety name or not. Its colors are bluish, white, or gray. The
various types differ in color due to metallic impurities, such as iron, nickel,
copper, and titanium, present during crystallization.
Agate is distinguished by having multiple colors. Banded agates are some of the
most popular. A rarity is the so-called fire agate. Fire agate: The iridescent colors
of red, gold, green and rarely, blue-violet, result from interference between light
rays traveling through these thin layers. Agate jasper, which grows together with
agate, is yellow, brown, or green blended. Agate comes in many different trade
names. The most important ones are: Dendritic agate: Colorless or whitish,
translucent chalcedony with tree- or fern-like markings (called dendrites). Moss
agate: Colorless with green, brown or red inclusions. Moss agate is a translucent
chalcedony with moss-like inclusions of hornblende or chlorite. Scenic agate:
Agate where the included dedrites resemble landscape-like images in brown or
reddish color tones. Onyx is a layered stone with a black base and a white upper
layer.
Bloodstone is an opaque, dark-green chalcedony with red spots (caused by iron
oxide).
Blue chalcedony, called "Mohave" and "Mt. Airy Blues", originate in California
and Nevada, are slightly to moderately grayish blue with a light to medium color
range. Blue chalcedony from Namibia, often called "African Blue", varies from
grayish to nearly pure blue and from light to medium dark. The most unusual and
most valuable type is from Oregon. Its blues are modified by slight to moderate
amounts of pink, making a noticeably lavender gem, which nonetheless is
called "Holly Blue."
Chalcedony, in the narrow sense, comes in bluish white or gray. Unicolored
chalcedony sometimes is called onyx.
Carnelian ranges in color from yellow-orange to rich, near reddish orange, to
orangey brown, and varies from semi-opaque to highly translucent. The color
agent is iron. The color can be enhanced by heating. Cornelian onyx is a layer
stone with a red base and a white upper layer.
Chrysoprase, apple green chalcedony that derives its color from nickel, is
ranging from nearly opaque to nearly transparent. Its color spectrum includes
olivey, to nearly pure greens of medium tone. Very fine, highly saturated pieces
have been successfully misrepresented as Imperial jade.
Chrysocolla Chalcedony, marketed as "Gem Silica" this relatively rare, blue to
blue-green, opaque to near transparent material is the most expensive type of
chalcedony. Its color agent is copper.
Quartz location and deposits
Quartz is one of the most common minerals on earth.
Macrocrystalline quartz deposits:
Rock crystal: In the Alps, Brazil, Madagascar, United States
Smoky quartz: Brazil, Madagascar, Russia, Scotland, Switzerland, Ukraine
Amethyst: Brazil, Bolivia, Canada, India, Madagascar, Mexico, Myanmar
(Burma), Namibia, Russia, Sri Lanka, United States (Arizona), Uruguay and
Zambia
Amethyst quartz: Brazil, Bolivia, Canada, India, Madagascar, Mexico, Myanmar
(Burma), Namibia, Russia, Sri Lanka, United States (Arizona), Uruguay and
Zambia
Ametrine: Brazil, Bolivia
Citrine: Argentina, Brazil, Madagascar, Namibia, Russia, Scotland, Spain, United
States
Prasiolite: Brazil, United States (Arizona)
Rose quartz: Brazil, India, Madagascar, Mozambique, Namibia, Sri Lanka, USA
Aventurine: Austria, Brazil, India, Russia, Tanzania
Prase: Austria, Finland, Germany, Scotland
Quartz cat's eye: Brazil, India, Sri Lanka
Hawk's eye: Brazil, India, Sri Lanka
Tiger's eye: Australia, India, Myanmar, Namibia, South Africa, Sri Lanka, United
States
Cryptocrystalline quartz deposits:
Australia: Agate, chrysoprase, bloodstone
Brazil: Agate, chalcedony, carnelian, bloodstone, chrysoprase
China: Agate, bloodstone
India: Agate, chalcedony, bloodstone, carnelian, chrysoprase
Kazakhstan: Chrysoprase
Madagascar: Agate, chalcedony, chrysoprase
Mexico: Agate
Mongolia: Agate
Namibia: Agate, blue chalcedony, chalcedony,
Russia: Chrysoprase
Sri Lanka: Chalcedony,
Uruguay: Agate, chalcedony, carnelian
South Africa: Chrysoprase
Tanzania: chrysoprase
Zimbabwe: Chalcedony, chrysoprase
USA: Agate (Montana and Wyoming), chalcedony (California), chrysocolla
chalcedony (Arizona), bloodstone, blue chalcedony (California, Nevada, Oregon)
Common Quartz treatments
Colorless quartz is always untreated. Colored stones can occasionally be
enhanced in color by dying (as in the case of agate), irradiation (bombardment
with low level radioactivity), or heating. Reliable gem dealers will always inform
their customers about any kind of treatment.
Quartz gemology
Species: Macrocrystalline Quartz
Chemical composition: SiO, silicon dioxide
The Quartz zodiac, myth & legend
Leonardo da Vinci wrote that amethyst, the most valuable stone in the quartz
family, was able to dissipate evil thoughts and quicken the intelligence.
Rock crystal and smoky quartz were once used for crystal balls that disclosed
fortunetellers, witches or gypsy grandmas the future of their clients.
Amethyst is the birthstone for those who are born in February, while Citrine is a
birthstone for November.
reflected in gemstones. The amethyst is assigned to planet Neptune. Citrine
is assigned to planet Mercury as well as tiger's eye. Rose quartz is assigned
to planet Venus. Chalcedony is assigned to Planet Saturn. Smoky quartz is
assigned to planet Pluto. The esoteric movement revived the ancient belief and
the gem industry made it another marketing tool to promote certain gems.
The healing powers of gems remain a controversial issue, but are mentioned
for centuries by healers, shamans and medicine men. Whether it's a fact or a
placebo effect doesn't matter, if it helps. The safest approach is to wear the
gemstone in skin contact to the troubled part of the body. Quartz is said to be of
great helping potential.
Headaches: Amethyst, rock crystal, tiger's eye
Eye inflammation: Rock crystal, chalcedony, hawk's eye, onyx
Sore throat: Rock crystal
Heart ailments: Rose chalcedony, rose quartz
Pancreas: Amethyst, citrine, yellow jasper
Sciatica: Amethyst, citrine, rose quartz, tiger's eye
Varicose veins: Rock crystal
Toenails: Rose quartz
Rhodolite Garnet
Rhodolite Garnet is the name applied to a mixture of almandite and pyrope.
Most probably the name rhodolite comes from the Greek word, "rhodon",
meaning rose.
The excellent hardness of 7 to 7.5 on the Mohs scale makes garnet suitable for
all kinds of jewelry. Garnet is the January birthstone.
Rhodolite Garnet location and deposits
Deposits are found in Brazil, India, Sri Lanka, Tanzania, Thailand and the USA
{North Carolina).
Species: Garnet
Color: Red with violent tint
Chemical composition: Fe3Ai2 (Sio4)3 iron, aluminum, silicate
Crystal system: (Cubic), rhombic dodecahedron, icons tetrahedron
Hardness: 6.5 - 7.5 (Mohs scale)
Ruby
Ruby is red corundum, all other color varieties of corundum being referred to
as sapphire
Ruby is named after the Latin word "ruber" for red. Rubies range in color from
pinkish to orangey and purplish and brownish red, depending on the chromium
and iron content of the stone. The most desirable color is the so-called "pigeon's
blood", a pure red with a hint of blue, only found in the mines of Myanmar
(Burma), the most important ruby deposits known.
Ruby is one of the most expensive gems, large rubies being rarer than
comparable diamonds. Many rubies are an essential part of royal insignia and
other famous jewelry.
Ruby is the birthstone for those who are born in July. Ruby is also used to
celebrate a couple's 15th and 40th anniversary.
Ruby location and deposits
Myanmar: For centuries the most important deposits are in upper Myanmar
(Burma) near Mogok. Only one percent of the production is of gem quality. Some
of the rubies are of pigeon's blood color and considered to be the most valuable
rubies of all. In the early 1990's large new deposits were discovered at Mong
Hsu.
Thailand: Rubies found in Thailand (Chanthaburi district) often have a brown or
violet tint. The Thai ruby production is declining, and Chanthaburi is now mainly a
center for processing and trading gems.
Sri Lanka: The deposits are located in the southwest of the island in the
Ratnapura district. Rubies from that deposits are usually light red to raspberry
red.
Tanzania: On the upper Umba River in northwest Tanzania are deposits for
gemstone quality rubies that are violet to brown-red. A few opaque rubies are
mined as well.
Other deposits of some importance are found in: Afghanistan, Cambodia, Kenya,
Madagascar and Vietnam. Less significant deposits are in: Australia, Brazil,
India, Malawi, Nepal, Pakistan, United States and Zimbabwe.
Common Ruby treatments
The most common treatment for ruby is heat treatment. Stones, generally before
they are cut, are heated to between 1700 to 1800 degrees Celsius (3100-3300
degrees F) for several hours. Heating often improves both color and clarity. A
reputable dealer will always disclose gem treatments.
Lower grade rubies with surface-reaching fissures are often fracture-filled with
lead glass. This treatment produces good looking stones that can be sold at a
very reasonable price.
Ruby gemology
Species: Corundum
Color: Varying red
Chemical composition: Al2O3 aluminum oxide
Crystal system: (Trigonal) hexagonal prisms or tables, rhombohedrons
For a long time India was considered as the classical source of rubies. In
the Sanskrit language ruby is called "ratnaraj", which translates as "King of
Gemstones".
In ancient times one of the chief attractions of ruby has been its protection from
misfortune and bad health.
Ruby is the birthstone for those who are born in July. On the Zodiac chart, ruby is
the stone for Capricorn.
Ruby is also used to celebrate a couple's 15th and 40th anniversary.
reflected in gemstones. The ruby is assigned to the planets Mars and Pluto.
Ruby-Zoisite
Ruby-Zoisite, also known as anyolite, is the natural combination of ruby and
zoisite crystals in a single specimen. Zoisite, the same mineral as tanzanite,
provides an earthy green and black color while ruby lends pink and red highlights
Ruby-Zoisite was first discovered in 1954 in Tanzania. The name anyolite derives
from the word for "green" in the native language of the Massai.
Ruby-Zoisite gemology
Species: Zoisite
Color: Green with black and opaque ruby inclusions
Chemical composition: Ca2Al3(Sio4)3(OH) calcium aluminum silicate
Crystal system: Orthorhombic, multifaced prisms, mostly striated
Rutilated Quartz
Rutile is a mineral composed primarily of titanium dioxide, TiO2.
Rutile is the most common natural form of TiO2. Two rarer polymorphs of
TiO2 are known:
§
§
anatase (sometimes known by the obsolete name 'octahedrite'),
a tetragonal mineral of pseudo-octahedral habit; and
brookite, an orthorhombic mineral.
Rutile has among the highest refractive indices of any known mineral and also
exhibits highdispersion. Natural rutile may contain up to 10% iron and significant
amounts of niobium andtantalum.
Rutile derives its name from the Latin rutilus, red, in reference to the deep red
color observed in some specimens when viewed by transmitted light.
Rutile is a common accessory mineral in high-temperature and highpressure metamorphic rocksand in igneous rocks.
Rutile is the preferred polymorph of TiO2 in such environments because it has the
lowest molecular volume of the three polymorphs; it is thus the primary titanium
bearing phase in most high pressure metamorphic rocks, chiefly eclogites.
Brookite and anatase are typical polymorphs of rutile formed by retrogression of
metamorphic rutile.
Within the igneous environment, rutile is a common accessory mineral
in plutonic igneous rocks, although it is also found occasionally in extrusive
igneous rocks, particularly those which have deep mantle sources such
as kimberlites and lamproites. Anatase and brookite are found in the igneous
environment particularly as products of autogenic alteration during the cooling of
plutonic rocks; anatase is also found formed within placer deposits sourced from
primary rutile.
Rutile in quartz
The occurrence of large specimen crystals is most common
in pegmatites, skarns and particularly granite greisens.
Rutile is found as an accessory mineral in some altered igneous rocks, and in
certaingneisses and schists. In groups of acicular crystals it is frequently seen
penetrating quartz as in the "fléches d'amour" from Graubünden, Switzerland.
In 2005 the Republic of Sierra Leone in West Africa had a production capacity
of 23% of the world's annual rutile supply, which rose to approximately
30% in 2008. The reserves, lasting for about 19 years, are estimated at
259,000,000 metric tons (285,000,000 short tons).[5]
Color
Reddish brown, red, pale
yellow, pale blue, violet, rarely
grass-green; black if high in
Nb–Ta
Crystal habit
Acicular to Prismatic crystals,
elongated and
striated parallel to [001]
Crystal system Tetragonal ditetragonal
dipyramidal
Twinning
Comon on {011}, or {031}; as
contact twins with two, six,
or eight individuals, cyclic,
polysynthetic
Cleavage
{110} good, 100 moderate,
parting on {092} and {011}
Fracture
Uneven to sub-conchoidal
Mohs
scalehardness
6.0 - 6.5
Sapphire
Sapphire The blue sister of ruby. Ruby and sapphire are the same material,
the mineral corundum, and the second hardest gemstone after diamond. Red
corundum is known as ruby, while all other colors are referred to as sapphire.
While blue is the classic sapphire color, sapphire is actually found in a wide
range of colors, including yellow, pink and green.
Sapphire colors
Blue is the most famous of the sapphire colors. The prized Kashmir and Burmese
sapphires have a deep blue that is intense and velvety. These sapphires are not
often seen on the market today. Sri Lankan and Madagascar sapphires are the
most common today, with a wide range of colors from light sky blue to dark blue.
Other producers of blue sapphire are Australia, Tanzania, Thailand, Cambodia,
and Montana.
Colorless corundum is rare as faint shades of color are nearly always present.
Many small white sapphires used in jewelry are synthetic.
Purple sapphire is rare, but found in Sri Lanka and Tanzania. Iron and titanium
impurities together may cause the purple hue of the stone.
Much yellow sapphire is on the lighter side. Heat treatment can produce a more
intense yellow golden color, and beryllium-treated sapphire may be a brilliant
yellow. These stones are found in Sri Lanka, Thailand, Australia, Tanzania and
Madagascar. The yellow color is caused by traces of iron in the stone.
Padparadscha is the Sinhalese word for a Sri Lankan lotus flower. This very
rare sapphire color should have a pink and orange color simultaneously.
Color, brilliance, size and clarity will determine the value of these stones. A
truepadparadscha will always have a hint of pink.
Many sapphires that appear green consist of fine alternating bands of blue
andyellow sapphire, which may be visible under the microscope. Green
sapphiresare found in Thailand, Sri Lanka, Australia, and Madagascar.
Sapphires come from Thailand, Sri Lanka, Madagascar, Tanzania and Australia.
The United States, Cambodia, Nigeria, Kenya and China also produce some
sapphires. Perhaps the most famous sources for sapphires are the Kashmir
region of India, and Burma. Discovered over 100 years ago, the Kashmir
sapphire has a lovely, velvety blue color prized by gem lovers. Burmese
sapphires can also be fine, but like the Kashmir region, these two areas today
produce very little material.
Today Sri Lanka and Madagascar produces most of the fine sapphires on the
market. You can find a wide range of beautiful blues, from soft sky blue colors
to deeply saturated hues. In addition, the Kanchanaburi region in Thailand and
the Pailin region in Cambodia are renowned for deep blue sapphires. Tanzania,
an old producer of sapphires in other colors, is now starting to produce blue
sapphire from new deposits in the south.
Common Sapphire treatments
The most common treatment for sapphire is heat treatment. Stones are heated
(generally before they are cut) to between 1700 to 1800 degrees Celsius (31003300 degrees F) for several hours. Most sapphires today are heated, and
the stones of rich blue that are not heated can command enormous prices in
today's market. Some blue sapphires may also be diffusion treated, though this
treatment is more common for star sapphires. Beryllium treatment is now being
used to produce stunning orange and red colors that were once rarely seen. All
sapphire treatments should be fully disclosed by any reputable dealer.
Sapphire gemology
Species: Corundum
Color: Blue, colorless, pink, orange, yellow, green, purple, black
Chemical composition: Al2O3, Aluminum Oxide
Crystal system: (Trigonal), doubly pointy, barrel-shaped, hexagonal pyramids,
tabloid shaped
Serpentine
Serpentine is the name used for several different aggregate structures which are
usually green, yellowish green, or brownish green in color. The finer serpentine
is cut as cabochons for gemstones, orcarved into decorative objects. Though
serpentine is sometimes confused with jade, serpentine is usually spotted or
veined.
The serpentine group includes as many as 20 different members. All the
serpentines are a basic magnesium silicate, with many containing iron as well.
Other elements may also be present in small quantities, including chromium,
nickel and cobalt.
Two basic structures for serpentine are usually distinguished -- antigorite (leafy
serpentine) and chrysotile (fibrous serpentine). The chrysotile minerals are
more likely to form serpentine asbestos, while antigorite forms cryptocrystalline
masses sometimes with a lamellar or micaceous character. Since asbestos fibers
are a health hazard only the antigorite form is used f
Most serpentine are opaque to translucent, with a hardness rating ranging from
2.5 to 5.5. Antigorite tends to be the harder variety.Serpentine is fairly light, with
a density of 2.44 to 2.62, slightly lower than quartz. Luster ranges from greasy to
waxy to silky. Serpentine is known to be susceptible to acids.
Serpentine varieties are found in many places in the world, including
Afghanistan, Burma, China, New Zealand, the USA, Canada, UK, Greece, Italy
and Norway.
Sillimanite Gemstones
Sillimanite is an aluminum silicate, related to bothandalusite and kyanite. In
fact these three minerals arepolymorphs -- they share the same chemical
composition but different crystal structures.Kyanite is formed in a lower
temperature/higher pressure environment, while andalusiteforms in lower
temperature/lower pressure conditions and sillimanite under higher temperatures/
higher pressures.
Sillimanite is named after the American chemist Benjamin Silliman (1779-1864).
Silliman was one of the first American professors of science and taught at Yale
University. He was originally trained as a lawyer and taught law at Yale. The
president of the university proposed that Silliman study chemistry and natural
history and assume a new professorship in the sciences at Yale. Silliman
became an important chemist and geologist and discovered the constituent
elements of many minerals. He was also the very first person to distill petroleum.
Sillimanite occurs in a number of colors, ranging from colorless to gray-white,
yellowish, brownish and bluish. Sillimanite is rarely transparent. Sillimanite also
occurs in a fibrous form sometimes known asfibrolite, so named because the
mineral appears like a bunch of fibres twisted together. Some of these fibrous
sillimanite display chatoyancy or the cat's eye effect, often in an attractive violetbrown shade.
Historically, sillimanite has been a rare gemstone, known mainly to collectors.
Deposits have been found in Burma, Sri Lanka, Kenya and the USA. Recent
finds in India have made sillimanite more widely available, though it is still
classified as a collector's gem.
Gemologically, sillimanite has a
6.5 to with
7.5 on the Mohs scale
pearly luster. It has a refractive index
1.684, approximately the same
spodumene. Its specific gravity is
placing it between apatite and
the density scale. Like diamond,
fluorite, sillimanite has perfect
Sillimanite Cat's Eye
hardness of
a vitreous
of 1.655 to
as
3.23-3.27,
diopside on
topaz and
cleavage.
Spinel
Spinel is a special gemstone in many ways. For centuries it was mistaken
forruby and gained undeserved fame. Today fine red spinel is more rare
than rubybut less valuable. That looks like a delayed revenge for its questionable
past.
Its name derivation is also ambiguous. Experts are undecided whether it derives
from the Greek word for "spark" or the Latin "thorn".
Although commonly thought of as red, spinel can be found in a range of beautiful
pastel shades. These outstanding shades of pink, purple, orange, blue, plus
every combination in between make spinels some of the most desirable stones in
the world.
Due to its excellent hardness (8 on Mohs scale) and high clarity spinel is a very
fine gem for jewelry of all kinds. Spinel is never treated in any way and continues
to be a great substitute for ruby and sapphire as well.
The coloring agents in spinel are iron, chromium, vanadium and cobalt. Within
the spinel group some trade names have become common:
Flame spinel: Bright orange to orange-red spinel
Balas spinel: Pale red spinel
Pleonaste: Dark green to blackish, opaque spinel
Hercynite: Dark green to black spinel
Grahnite: Blue, violet, or dark green to blackish spinel
Gahnospinel: Blue to dark blue or green spinel
Picotite: Brownish, dark green, or blackish spinel
Spinel occurs with ruby and sapphire mainly in important deposits found
in Cambodia, Myanmar, Sri Lanka and Thailand. Other locations are in
Afghanistan, Australia, Brazil, Madagascar, Nepal, Nigeria, Tadzhikistan,
Tanzania and the United States.
Spinel gemology
Species: Spinel
Color: Red, orange, yellow, brown, blue violet, purple, green, black
Chemical composition: MgAl2O4 magnesium aluminum oxide
Crystal system: (Cubic) octahedron, twins, rhombic dodecahedron
Strawberry Quartz
Quartz with red inclusions of iron oxide is more rarely found, and is often sold
under the name strawberry quartz or "red fire" quartz. Some specimens have
very fine inclusions, only visible under magnification, lending the quartz a more
or less uniformly strawberry color. Others have clearly visible inclusions and may
appear as clear quartz with reddish needles, flakes or spangles.
Strawberry quartz gets its color from
inclusions of various forms of iron
oxide. There are four different but
chemically related iron oxides that may
be found in quartz. They include
lepidocrocite (FeO(OH)), goethite (also
FeO(OH) but with a different crystal
structure), limonite (FeO(OH)*nH2O)
and hematite (Fe2O3).
Some material sold as strawberry quartz
is
synthetic rather than natural; most of it
is simply glass. Fruit Quartz is the
general trade term for a group of
colorful, translucent materials which are
individually known by names such
Click here to enlarge photo
as "cherry quartz," "blueberry
Strawberry Quartz from Russia
quartz," "strawberry quartz,"kiwi
quartz," "pineapple quartz," and so on.
They are commonly carved into jewelry components such as beads or pendants
or into decorative objects. But don't confuse these synthetic products with
genuine quartz with natural iron oxide inclusions.
Strawberry quartz is most often found in Russia and in neighboring regions such
as Kazakhstan, as well as in Brazil.
Sugilite
Sugilite is a rare mineral of fairly recent discovery. It is named after the
Japanese geologist, Ken-ichi Sugi, who first identified it in 1944. It has a
distinctive purple color and is usually opaque to translucent. Sugilite has
sometimes been called purple turquoise although there is no really no connection
at all between sugilite and turquoise.
Though sugilite was first discovered in 1944, it did not become of interest to
the gemstone world until many years later. In 1979 a major deposit of gemquality sugilite was found in a manganese mine in the Southern Khalahari desert
in South Africa. This important deposit yielded several thousand kilograms of
material.
In mineralogical terms, sugilite is classified as a cyclosilicate, in the same class
as tourmaline, iolite and the beryl group. Sugilite has a very complex chemical
composition, it is a Potassium Sodium Lithium Iron Manganese Aluminum
Silicate. It is only rarely found as crystals, usually being massive in form. Sugilite
has a Mohs hardness of 5.5 to 6.5 and a specific gravity of 2.75-2.80. It has
a refractive index of 1.607-1.61 and typically has a vitreous to waxy luster. Not
especially hard, sugilite is quite a durable material since it has poorcleavage.
Sugilite gemstone colors include all shades of
purple -- from lilac to plum, including hues of
magenta, purple and red violet. Sugilite
specimens often contain black matrix, and
reddish or yellowish blotches, since the mineral
sugilite occurs in brownish yellow and pale pink
as well as violet and reddish violet. Sugilite
cabochons will often be found mixed with
chalcedony.
Sugilite Square Cabochon
Like most colored stones,
based on its color. Specimens
intense purple are valued most
many sugilite specimens are
Sugilite Trillion
Cabochon
attractive
patterns
and veining
of a piece. Sugilite is often
sizes, with pieces over 10 carats being common.
Sugilite deposits
are found in
Australia, India,
Japan, Canada
and South Africa.
sugilite is valued
with a vivid and
highly. Since
multicolored, the
will raise the value
available in large
Sunstone
Sunstone belongs to the plagioclasefeldspar group, and is named for its unusual
spangled or glittery appearance. Its proper mineralogical name, however,
is aventurine feldspar, named from a type of glass made with copper that was
discovered by chance (from the Italian, a ventura). This is one of the rare cases
where the name of a natural stone came from its synthetic simulant.
Aventurine is the name used for both a type of green quartz and a golden
feldspar. Both have a metallic glittery appearance caused by inclusions. The
spangled effect is known as aventurescence. Perhaps to avoid confusion, the
name sunstone has been adopted in the gem trade for the feldspar, while the
name aventurine (or aventurine quartz) is used for the quartz variety.
Sunstone is typically a red-brown hue, with a metallic glitter which is caused
by tiny platelets of hematite or goethite. The glitter is usually gold or red,
but very occasionally green or blue. We have found both opaque and
transparent/translucent specimens in the market. The opaque material is cut
as cabochons while the transparent material can be faceted. Some of the
cabochons will display a discernible star effect and are sold under the nameStar
Sunstone.
Sunstone is a sodium calcium aluminum silicate, with a hardness of 6-6.5 on
the Mohs scale. It has a density of 2.62-2.65 and a refractive index of 1.5251548. It has perfect cleavage.
Sunstone deposits are found in India, Canada, Madagascar, Norway, Russia and
the USA. In 1987 sunstone was named the state mineral of the state of Oregon
in the USA. The Oregon sunstone is rather unique in that it is the only sunstone
containing copper crystals.
Sunstone has been known for many centuries and has been discovered in Viking
burial mounds. Sunstone was thought to have magical properties and could be
used to invoke the energies associated with the sun. In ancient Greece, it was
thought to represent the sun god, bringing life and abundance to those fortunate
enough to own it. The native people in Oregon used it for trade and barter.
Tanzanite
Tanzanite was enthusiastically celebrated as "Gemstone of the 20th Century"
after its discovery in 1967. It is named after the East African state of Tanzania
where its only deposit has been found. The legendary New York jewelers Tiffany
& Co were the first to promote tanzanite as a fine gemstone.
Tanzanite is a variety of the zoisite species. In good quality the color is
ultramarine to sapphire blue. The most popular color is a saturated blue, which
shows a purplish hue shimmering around it.
The only known deposit of tanzanite is a five square mile hilltop at Merelani Hills
near Ausha, ten miles south of the Kilimanjaro International Airport in Tanzania.
Most rough crystals show a large proportion of brownish-yellow tints, which
vanish when heated to 752-932 degrees F (400-500 degrees C).
Tanzanite gemology
Species: Zoisite
Color: Sapphire blue, amethyst, violet
Chemical composition: Ca2Al3(Sio4)3(OH) calcium aluminum silicate
Crystal system: Orthorhombic, multifaceted prisms, mostly striated
Birthstone for December
Topaz
Topaz of any type is a good jewelry stone and it is historically one of the most
important gemstones. With its relatively high refractive index and hardness
of eight (Mohs scale), with no special sensitivity to chemicals it can be used,
with appropriate care (should be protected from hard knocks), in any jewelry
application.
and blue. The blue topaz, with a pale to medium blue color created byirradiation,
to reddish. The coloring agents are iron and chromium.
The name topaz is most probably derived from an island in the Red
Sea, "Topazos", today called Zabargad, the ancient source of peridot. In former
times all golden-brown and sometimes also green gemstones were called
topaz, which caused sufficient confusion such that today real topaz is referred to
as precious topaz.
Topaz is the birthstone for those who are born in the month of November.
Topaz location and deposits
Brazil (Minas Gerais) is the most important supplier for topaz. Other deposits
are in Afghanistan, Australia, China, Japan, Madagascar, Mexico, Myanmar,
Namibia, Nigeria, Pakistan, Russia, Sri Lanka, Ukraine, United States and
Zimbabwe. Natural light blue topaz is also found in England (Cornwall), Northern
Ireland and Scotland.
Common Topaz treatments
Blue topaz begins as colorless or very lightly tinted natural topaz crystals, which
are then irradiated to change the color to blue and heated to stabilize the change.
Neutron bombardment in a nuclear reactor produces the deep slightly greenish
or grayish "London Blue", while electron bombardment in a linear accelerator
results in the light aqua-like blue known as "Sky Blue". Combinations of both
treatments produce the highly saturated "Swiss" and "Electric" blues. If neutron
bombardment has been used, there is residual radioactivity, and the gems must
be held, up to a year, before they have "cooled" enough to be worn.
In general, blue topaz is modestly priced. Due to the expenses of reactor time the
London Blue color is short in supply and climbs in value.
In early 1998, a new type of enhanced topaz made its appearance, the surfaceenhanced topaz, with colors described as blue to greenish-blue or emerald
green.
The vast majority of pink topazes are heat-treated yellow stones that turn pink.
Topaz gemology
Species: Topaz
Color: Colorless, yellow, orange, red-brown, light to dark blue, pink-red, red,
violet, light green
Chemical composition: Al2SiO4(F2OH)2 fluor containing aluminum silicate
Crystal system: Orthorhombic, prisms with multi-faceted ends, often eight-sided
in cross-sections along length
Tourmaline
One of the most versatile of gemstones, tourmaline is available in every color,
from colorless to black. You can find every tone from pastel to dark, and even
with one or more colors appearing in the same stone. It truly is a wondrous and
fascinating stone!
Known for centuries, tourmaline first gained popularity when the Dutch began
to import it in the early 17th century from Sri Lanka . They gave the gem a
Sinhalese name, Turamali, which is believed to mean stone with mixed colors.
Tourmaline is actually the name of a group of related mineral species. In
gemological practice, individual species names are not used. Instead, all
are simply termed tourmaline. Tourmaline commonly comes from Tanzania,
Madagascar, Brazil, Australia, Sri Lanka, the U.S., and Russia, plus other
Color is the major characteristic for tourmaline. This stone is found in morehues,
shades and nuances than any other gem. Here are some of the most common
varieties that are recognized in the gem trade.
Rubellite – Varying in color from mid to deep reds resembling ruby, rubellite is
one of the rarest and most valuable tourmalines. Many gems in the 17th century
Russian Crown jewels, originally thought to be rubies, are actually rubellite
tourmalines.
Indicolite – From bright blue hues to bluish green colors, indicolite tourmaline is
another rare tourmaline color, and high quality specimens are regarded as quite
collectable.
Chrome – Chrome tourmaline is green, but is considered different from the
regular greens as it derives it rich green color from trace elements of chromium.
Found in East Africa , chrome tourmaline is rare and is usually found only in
smaller sizes.
Bi-Color – Variations, zones and color bands in tourmaline are often purposefully
accented with the cutting style to show bands and color zones in the gem.
Occurring in uncountable colors variations, these are often seen in long acicular
crystals.
Watermelon – Bi-color tourmalines which show a green skin and a red core;
these are sometimes cut as slices
Canary – Bright yellow tourmaline from Malawi .
Paraíba – A rare blue-green tourmaline containing copper, Paraiba
tourmalinecan be found in amazing bright neon hues and can command
thousands of dollars per carat. Found in a single area in Paraiba, Brazil, it
is generally found in comparatively small sizes for tourmaline. Recent finds
of copper content tourmaline in Nigeria and Mozambique have also produced
similar bright neon tourmaline.
Cat's Eye – Chatoyant tourmaline in a variety of colors. It is often found in a rich
green.
Color-Change – Changes from green in daylight to red in incandescent light.
Other varieties may be simply sold with a color prefix, as in pink tourmaline. Like
most gems, you want the color to be as intense as possible, however, not too
dark or too light.
Tourmaline has strong pleochroism , which means you can see different colors
or depths of color when viewed at different angles, such as when you rotate the
stone in the light.
Tourmaline Gemology
Color: Colorless, pink, brown, red, yellow, green, blue, black, violet, multi-colored
Moh's Harness: 7-7½
Zircon
Zircon is known since the Middle Ages. The oldest known zircons are from
Western Australia, with an age of 4.4 billion years. The name probably
comes from the Persian word "zargun" which means "gold-colored,"
although zirconcomes in a wide range of different colors. The most popular
zircon-color is blue.
Zircon is a birthstone for those who are born in December.
Colorless when pure, the zirconium silicate takes on various shades due to
impurities. The most popular zircon-color is blue. Most blue gemstones come in
a pastel blue, but some exceptional gems have a bright blue color. Zircon is also
available in green, dark red, violet, yellow, brown, and orange.
The brown varieties, mostly found in Southeast Asia, are heat treated in order to
produce colorless and blue zircons.
In the gemstone trade some terms refer to different colored zircons:
Hyacinth: yellow, yellow-red to red-brown zircon
Jargon: straw-yellow to almost colorless zircon
Starlight: rich, slightly greenish blue zircon variety, created by heating
Zircon location and deposits
Zircon deposits are mainly alluvial. Zircon is found in Australia, Brazil, Cambodia,
Korea, Madagascar, Mozambique, Myanmar, Nigeria, Sri Lanka, Tanzania,
Thailand and Vietnam.
Common Zircon treatments
The brown varieties, mostly found in Southeast Asia, are heat treated at
temperatures of 800-1000 degrees C (1472-1832 degrees F), in order to produce
colorless and blue zircons. These colors aren't necessarily stable. Ultraviolet rays
or sunlight can produce changes.
Zircon gemology
Species: Zircon
Color: Colorless, yellow, brown, orange, red violet, blue, green
Chemical composition: ZrSiO4 zirconium silicate
Crystal system: (Tetragonal), short, stocky, four-sided prisms with pyramidal
ends
Hardness: 6.5-7.5 (Mohs scale)

Traditional Birthstone Calendar Month Genuine Cabochon

Transcription

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