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A
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Showcasing selections from the
ROSS LILLIE COLLECTION
of Illinois Minerals
TOM WOLFE Calcite Collection
DR. ART SOREGAROLI Collecion
Mindat Madagascar
Symposium Trip Report
Page
5
By
Ida Chau
Mindat.org
Page
7
By
Prof. Jens Göetze
TU Bergakademie Freiberg
Page
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25
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35
Find your OwnAgate Collecting around
Kremmling Colorado
Morocco - The Country,
The People and...Agates
By
Holger Quellmalz
Crystal Days in
Lwówek Śląski
By
Jolyon Ralph
Mindat.org
Agates and
Associated Minerals of
Creede Colorado
By
Philip Persson
PerssonRareMinerals.com
Mindat was founded almost exactly 20 years ago
by Jolyon Ralph. In the growth years, which still
include today, every aspect of Mindat’s interest
areas have grown. Recently, Gemdat has
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for the gem industry and practitioner. There are
many plans to further expand the scope of the
spectrum of related programs and services and
a major funding program has been established
to be able to allow Mindat services to increase.
Please visit us at www.mindat.org. The “.org”
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a “.com”, a general or commercial website.
Mindat Show Special V.1 #2 2014
Cover Image:
“Saturn’s Rings”
Inclusions in Agate
Photo and Collection of
Tom Shearer
3
Agates and
Associated Minerals
Mindat is a free worldwide technical resource
that has been created by worldwide amateur
and professional mineralogists who range from
first-day collectors through voting members
of the International Mineralogical Association.
The board of Mindat managers edit and verify
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Mindat
Show Special
Denver 2014
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All Articles and Photographs - Copyrights Reserved 2014 - Printed in Denver, Colorado
IDA CHAU’S
JOURNAL FROM THE
3RD MINDAT INTERNATIONAL
CONFERENCE
Mindat 3rd International Conference
May 28th to June 13th, 2014 started at
Madagascar capital city Antananarivo.
The First Day we drove to the town
Antsirabe and visted the Tritiva Lake
and the local mineral market.
The second day we drove to the Mahaiza Village
to visit the local market. We bought some
minerals and then went to the Tsaramanga
Pegmatite for blue beryl, big columbite crystals
and rose quartz.
Day 3 we visited pegmatites
in Sahatany Valley, a famous
area for multi-color
tourmaline, beryl and
spodumene.
The next two
days, we went to
Ambatonapetraka pegmatite
collecting the tourmalines and then
drove to Ihasofotsy village to see lots of
wonderful quartz crystals.
June 3rd & 4th, we drove to nearby Ivato, a gold
locality. In the evening we visited the famous
Ranomafana National Park We drove to Anja
Park and saw lemurs and
wonderful landscapes.
June 5th,
this day included a long hard walk
to the Amboarohy corundum quarry.
Amboarohy is the famous locality for
sapphire and ruby.
The next two days we stayed at some local
luxury hotels, visited the Isalo Park and also at
night time we have Frederico Pezzota give us an
expert talk for this conference.
June 7th, we went to Ilakaka sapphire deposit
and visiting the working and lapidary shops.
The next two days we in Ambolimalika enjoying
the swimming and watching the fishermen.
We continue our journey, drive to Tulear and took
the flight to Morondava and keep going a long days
on lots of bad roads and two ferrys. We stopped at
Avenue de Baobab and took lots of pictures.
The last two days of conference we visited to the big
and small Tsingy in Tsingy de Bemaraha which was the
highlight of my trip.
What a wonderful experience of my lifetime! Special
thank you to Tom Praszkier, Giorgio, Sergico Malala,
Tony and Noro for all their hard work, and thank you
to Mindat members who attended our
mindat 3rd conference.
Minerals in volcanic agates
Minerals in agates
Prof. Jens Göetze, Mineralogist
TU Bergakademie Freiberg, Germany
Introduction
Agates are some of the most
fascinating mineral objects in
nature because of their wide
spectrum of colors, hardness, and
spectacular forms. Therefore,
they play a dominant role as
gemstones and cut stones since the
ancient world, and still popular
stones for collectors worldwide,
today. Although agates use for
amulets and jewelry has been in
fashion since ancient times, the
question concerning the genesis
of agate is still in discussion today.
Both in historic and recent time
many speculations have been
made about this topic.
Several monographs and a lot
of data about certain agate
occurrences or specific aspects
of agate formation have been
published during the last 20-30 years
(e.g., Landmesser, 1984; Godovikov et
al., 1987; Blankenburg, 1988; Moxon,
1996, 2009; Pabian and Zarins, 1994;
Zenz, 2005, 2009, 2011; Colburn,
2008, Clark, 2009; Götze, 2011),
which significantly increased our
knowledge about the mineralogy
and genesis of agates.
7
The results document that agate
formation is a very complex and
often a multi-step process, which
can vary for agates in volcanic
rocks, hydrothermal vein agate
or sedimentary agates (Götze,
2011).
Many field observations and
analytical
results
document
that besides the different silica
minerals, numerous other mineral
phases are formed pre-, syn- and
post-genetically with the agates.
Depending on the type of host
rocks and the time of formation
these minerals can occur as
mineral inclusions in quartz,
paragenetic minerals intergrown
with SiO2, or pseudomorphs.
An excellent compilation of
inclusions in agates is given by
McMahan (2009) in “Agates II”.
The
following
explanations
provide an overview about
minerals in agates, their formation
and the genetic importance for
the process of agate genesis.
Table 1 Compilation of minerals in
volcanic agates (data according to
Godovikov et al., 1987; Blankenburg,
1988; Holzhey, 1993; Pabian and Zarins,
1994; Cross, 1996; Moxon, 1996; Götze
et al., 2001; Möckel and Götze, 2007)
Agate formation in volcanic rocks
is the most abundant process
of agate genesis. It is assumed
that the silica necessary for the
formation of agates originates
from alteration processes of the
volcanic host rocks. Therefore,
many of the minerals present in
or together with agates can also
be related to these alteration
processes (Table 1).
Blankenburg (1988) reported
a significant difference in the
frequency of associated minerals
in basic or acidic volcanic rocks.
The mineral spectrum in agates
of basic volcanic rocks is much
wider. It is obvious that minerals
of more or less all mineral
classes are present: elements,
sulfides,oxides/hydroxides,
carbonates, sulfates, phosphates,
halides and of course silicates.
The observed mineral associations
(and their stability fields) in
volcanic agates indicate a preferred
formation under hydrothermal
and low temperature conditions.
Most of the minerals can be related
to the alteration processes of the
volcanic host rocks. Especially
the most frequent mineral phases
such as clay minerals, zeolites,
iron
oxides/hydroxides
and
carbonates represent products of
these decomposition reactions and
emphasize that besides enormous
amounts of SiO2 also Al, Fe, Ca,
Na and K are released during
these processes. The presence of
water- and OH-bearing minerals,
carbonates and fluorite in volcanic
agates emphasizes the role of
H2O, CO2 and F-complexes as
main volatile compounds for the
transport of substances (Götze et
al. 2012).
Mineral Group
Minerals
Elements
Sulfides
Oxides/Hydroxides
copper, lead, graphite
pyrite, marcasite, sphalerite, chalcopyrite, galena
hematite, goethite, todorokite, ramsdellite, birnessite, pyrolusite, rancieite, hollandite, cryptomelane psilomelane
calcite, dolomite, siderite, aragonite, rhodochrosite,
strontianite, magnesite, malachite
barite, celestite, anhydrite, gypsum
apatite (variety dahllite), monazite
fluorite
clay minerals, zeolites, glauconite - celadonite series,
chlorite, serpentine, talc, prehnite, datolite, epidote,
apophyllite, chrysocolla
Carbonates
Sulfates
Phosphates
Halides
Silicates
Carbonates, especially calcite
(CaCO3), are some of the most
frequent minerals found in
volcanic agates. In many cases,
coarse-grained calcite has been
formed as overgrowths on quartz
or chalcedony in the central part
of the agate geodes (Fig. 1a), but
calcite layers intergrown with
chalcedony are also possible (Fig.
1b). A special case is the so called
“calcite agate” (Walger, 1961;
Landmesser 1996), an “agate”
completely
consisting
of
calcite (Fig. 1c). Geochemical
investigations on calcite in
agates showed sometimes several
carbonate generations and proved
a temperature of crystallization
in the range between ca. 20 and
230°C (e.g., Blankenburg, 1988;
Schmitt-Riegraf, 1996; Götze
et al. 2001), which confirms the
estimated temperatures of agate
formation.
A
remarkable
feature
in
worldwide agate occurrences is
the appearance of iron-bearing
phases in agates, indicating high
concentrations of iron in the
mineralizing fluids. Different
types of iron oxides and
hydroxides in the marginal parts
of the agates as well as within
the chalcedony matrix cause
the typical colorations in red,
brown and yellow. In addition,
enrichment of iron compounds in
form of crusts or earthy masses in
the central parts of agates can be
observed.
At least three different types
of iron oxides (hydroxides) can
be distinguished, which are
closely connected with the
agate formation. Iron oxides
(e.g. hematite) of probably preor syngenetic formation often
appear at the interface between
host rock and agate or in the
outermost
chalcedony
layer
(Fig. 2a/b). The crystals show
spherulitic as well as acicular
or dentaloid forms, the latter
probably originating from the
replacement of former existing
carbonates (pseudomorphs).
Fig. 2 Iron-bearing mineral phases in agate:
Fig. 1 Occurrence of different forms of carbonate in agates:
9
a – euhedral calcite crystals in the central void of an agate geode from
St. Egidien, Germany.
b – intergrowth of speherulitic carbonate with chalcedony in an agate
from Ojo Laguna, Chihuahua (Mexico).
c – geode completely filled with calcite (so called “calcite agate”) from
Duchroth-Talböckelheim, Germany (after Landmesser, 1996).
a – spherulitic iron oxides at the interface between host rock and an agate
from Rancho Coyamito, Chihuahua (Mexico)
b – needle-like iron-bearing minerals in the outer part of a “Lava Cap”
agate from Deming, New Mexico (USA)
c – globular aggregate of iron oxide within the chalcedony matrix of an
agate from St. Egidien, Germany.
10
Two further types of iron oxide
inclusions have been observed
within the agate matrix. One
type is laminated and lenticular
agglomerates of very small
hematite particles (<10 µm)
occur, whereas the other type is
represented by larger, sometimes
globular or irregular aggregates of
up to several 100 µm in size (Fig 2c).
The fine-grained particles were
probably released from the silica
matrix during crystallization,
moved together with the growth
front and accumulated along the
banding. In contrast, larger iron
oxide inclusions show interesting
structures consisting of several
rounded disks. These structures
indicate that the iron oxides
neither existed before the
crystallization of the chalcedony,
nor have been incorporated later.
Most likely, iron oxides and silica
precipitated simultaneously from
a precursor gel.
Besides carbonates and iron
oxides, a number of other mineral
phases crystallized in agates
(Table 1). It is noteworthy, that
certain chemical elements may
be present in different chemical
compounds in the same agate.
For instance, native copper can
occur together with copper oxide
and copper sulfide, or pyrite/
marcasite in association with
iron oxides/hydroxides in agate
geodes (Fig. 3). This is an evidence
for strongly varying physicchemical conditions (especially
redox conditions) during mineral
formation.
The different successions and
stability fields of minerals
result in a wide variety of
inclusions and replacements of
earlier existing phases in agates
(e.g.,
pseudomorphism
and
perimorphism). Pseudomorphism
(Greek “pseudo” = false) occurs
when a mineral is transformed
to or replaced by another
mineral by perpetuation of its
original crystallographic shape
(Fig. 4a). Perimorphism (envelope
pseudomorphism) is formed by
overgrowth of a mineral with a
secondary one, followed by the
dissolution of the original mineral
(Fig. 4b).
Pseudomorphism
of
quartz
was mostly detected after
carbonates (calcite, aragonite)
and sulfates (barite, anhydrite/
gypsum), but also after zeolites
and pyrite (e.g., Godovikiov et
al., 1987, Blankenburg, 1988;
Cross, 1996). The earlier existing
minerals have been replaced by
SiO2-rich fluids (Fig. 5). In most
cases the original minerals are
completely removed and the
former mineral is determined
on basis of its preserved crystal
shape. One of the best known
examples of pseudomorphism is
the occurrence of the well known
Paraiba agates in Brazil, which
crystallized in almost perfect
shapes in interstices of formerly
existing calcite. In general,
pseudomorphism occurs not only
in volcanic agates but is also
common in hydrothermal vein
agates and sedimentary agates.
Fig. 3 Agate from Steinbach, Saarland (Germany) with marcasite
(arrows) in the marginal part and iron oxides in the red central parts
of the agate.
Fig. 4 Schematic sketch showing the processes of (a) pseudomorphism
by replacement of mineral A by mineral B with perpetuation of its
original crystallographic shape, and (b) perimorphism by overgrowth of a
mineral with a secondary one, followed by the dissolution of the original
mineral.
12
Minerals in hydrothermal vein agates
Fig. 5 Pseudomorphs in agates from Liebgensmühle (Saxony, Germany)
showing different appearance.
Only in some cases relics of the
primary minerals are detectable
using highly advanced analytical
methods. Figure 6 shows a
sample of agate pseudomorphs
from
Liebgensmühle
near
Leisnig (Saxony, Germany) with
inclusions of elongated shape.
Microscopic investigations with
cathodoluminescence revealed
relics of primary dolomite and
inclusions of kaolinite probably
from alteration processes (Fig.
6c). However, most of the
agate consists of quartz and
chalcedony.
Fig. 6 (a) - Pseudomorphic mineral formation in an agate from Liebgensmühle
(Saxony, Germany); detailed investigations with polarizing microscopy (b)
and cathodoluminescence (c) revealed relics of dolomite in the core of the
lath-shaped crystals as well as fine kaolinite from alteration processes.
The genesis of vein agates
represents a completely separate
form of agates.
Hydrothermal vein agates can
be formed in non-volcanic rocks
directly within veins and fissures
of the crystalline host rocks
from circulating hydrothermal
solutions. In contrast to the agates
from volcanic rocks, the genesis
of vein agates is associated with
hydrothermal processes (i.e. with
hot aqueous solutions/fluids) by
filling of fissures and cavities,
which were present or have been
formed by tectonic processes
during magmatic activities. In
these fissures and joints, SiO2
minerals can precipitate and
crystallize together with a
number of other hydrothermal
minerals. These are in particular
carbonate and sulphate minerals
such as calcite (CaCO3) or barite
(BaSO4), but also fluorite (CaF2)
or certain ore minerals (oxides,
sulphides of lead, zinc, copper,
uranium, etc.).
Due to their high solubility, calcite
and barite can be dissolved
and/or replaced by quartz
resulting in typical replicas or
pseudomorphs. Such secondary
formation is frequent in vein
agates and exhibits different
morphological forms. The wellknown Crazy Lace agates from
Chihuahua, Mexico often show
spectacular pseudomorphic forms
after calcite. Because of their
characteristic shapes, which
resemble teeth, Cross (1996)
called them pseudomorphs after
“dogtooth calcite“ (Fig. 7a). Platy
forms (so called lattice bladed)
can trace the original flaky crystal
shapes of carbonates or sulphates
(Fig. 7b).
Fig. 7 (a) - Crazy Lace agate from Durango, Mexico with typical dogtooth
texture, i.e. pseudomorphism of quartz after calcite; (b) – hydrothermal
vein agate from Cerny Halze (Czech Republic) showing pseudomorphs
(carbonate/sulphate) with lattice bladed texture.
14
Summary
Minerals in sedimentary agates
In many sedimentary rocks
of the Earth crust agates are
formed by filling of cavities and
empty pore space with SiO2 or
the silicification of concretions
and pseudomorphism (Petranek,
2009). It is assumed that these
processes take place during
sedimentation or early diagenesis,
when enough moisture is within
the sediment. Pseudomorphism
occurs by stepwise replacement
of soluble mineral species such
as sulphates (e.g. anhydrite) or
carbonates (calcite, dolomite)
by SiO2 (compare Fig. 4). These
processes can be detected by
relic structures and/or residues of
calcite or anhydrite in the center
of the geodes.
A couple of characteristic mineral
associations can be found in
sedimentary agates.
Large crystals of quartz, calcite,
celestine or barite can form
in the centre of the geodes.
Within the agates, carbonates
(calcite,
dolomite,
ankerite,
aragonite, smithsonite), sulphates
(barite,
gypsum),
sulfides
(pyrite, marcasite, chalcopyrite,
sphalerite), native sulfur, FeMn-oxides/hydroxides (goethite,
hematite, limonite, pyrolusite),
and malachite were detected
(e.g., Tripp, 1959; Hayes, 1964;
Petranek, 2009). Clay minerals
such as kaolinite, illite, chlorite,
palygorskite or montmorillonite
are common. Götze et al. (2009)
found fluorite and rare-earthelement carbonates in geodes of
the famous Dryhead agates from
Montana (Fig. 8).
References
Blankenburg, H.-J. (1988) Achat. VEB Deutscher Verlag für
Grundstoffindustrie, Leipzig.
Clark, R. (2009) South Dakota’s State Gemstone – Fairburn
Agate. Silverwind Agates, Appleton.
Colburn, R.P. (2008) The formation of thundereggs. CD, Geode
Kid Productions, Deming.
Fig. 8
Sedimentary
Dryhead agate
from Montana
(USA);
the close up
shows a violet
fluorite cube,
which belongs
to a late
mineralization
sequence.
15
During agate formation, numerous
other mineral phases are formed
pre-, syn- and post-genetically
with the silica phases. Depending
on the type of host rocks and the
time of formation, these
minerals can occur as mineral
inclusions in quartz, paragenetic
minerals intergrown with SiO2,
or pseudomorphs. Their size can
range from microscopic inclusions
up to several cm in size. Because
of the common occurrence
of certain minerals in agates,
they can significantly influence
their color, appearance and
properties.
Cross, B.L. (1996) The agates of Northern Mexico. Burgess
Publishing Division, Edina, Minnesota.
Godovikov, A. A., Ripinen, O. I., Motorin, S. G. (1987) Agaty.
Moskva, Nedra.
Götze, J. (2011) Agate – fascination between legend and
science. In: Zenz, J. (ed.) Agates III. Bode-Verlag, 19133.
Götze, J., Tichomirowa, M., Fuchs, H., Pilot, J., and Sharp, Z.
(2001) Geochemistry of agates: a trace element
and stable isotope study. Chemical Geology, 175, 523–541.
Götze, J., Möckel, R., Kempe, U., Kapitonov, I., Vennemann,
T. (2009) Origin and characteristics of agates in
sedimentary rocks from the Dryhead area, Montana/USA.
Mineralogical Magazine, 73, 673-690.
Götze, J., Schrön, W., Möckel, R., Heide, K. (2012) The role of
fluids in the formation of agate. Geochemistry,
72, 283-286.
Hayes, J.B. (1964) Geodes and concretions from the
Mississippian Warsaw Formation. Keokuk region, Iowa,
Illinois, Missouri. Sedimentary Petrology, 34, 123-133.
Holzhey, G. (1993) Vorkommen und Genese der Achate und
Paragensemineralien in Rhyolithkugeln aus
Rotliegendvulkaniten des Thüringer Waldes. Unpuplished PhD
thesis, TU Bergakademie Freiberg.
The spectrum of associated
minerals can significantly vary in
dependence on the genetic type
of agate. These differences can be
related to the different geological
background and differences in the
conditions of mineralization (e.g.
type of fluids).
Carbonates (especially calcite)
and iron oxides/hydroxides are
present in more or less all types
of agates, whereas clay minerals
and minerals of the zeolite group
are typical phases in volcanic
agates.
Landmesser, M. (1984) Das Problem der Achatgenese.
Mitteilungen Pollichia, 72 (5), 5-137.
Landmesser, M. (1996) Calcitachat: Zur Deutung eines
verblüffenden mineralogischen Phänomens. Mainzer
Naturwissenschaftliches Archiv, 34, 9-43.
McMahan, P. (2009) Inclusions in agate. In: Zenz, J., Agates II.
Bode-Verlag, Haltern, 516-637.
Möckel and Götze (2007) Achate aus sächsischen Vulkaniten
des Erzgebirgischen Beckens. Veröffentlichung
Museum für Naturkunde Chemnitz, 30, 25-60.
Moxon, T. (1996) Agate: Microstructure and possible origin.
Doncaster: Terra Publications.
Moxon, T. (2009) Studies on agate – microscopy, spectroscopy,
growth, high temperature and possible origin.
Terra publications, Auckley, Doncaster, S. Yorks.
Pabian and Zarins (1994) Banded agates – Origins and
inclusions. Educational Circular No. 12, University of
Bebraska, Lincoln.
Petranek, J. (2009) Sedimentäre Achate. Der Aufschluss, 60,
291-302.
Schmitt-Riegraf, C. (1996) Magmenentwicklung und spät- bis
post-magmatische Alterationsprozesse permischer
Vulkanite im Nordwesten der Nahe-Mulde. Münstersche
Forschungen zur Geologie und Paläontologie,
80, 1-251.
Tripp, R.B. ((1959) The mineralogy of Warsaw Formation
geodes. Iowa Academic Science Proceedings, 66,
350-356.
Walger, E. (1961) Zur Entstehung
Fortschritte Mineralogie, 39, 360.
des
Calcitachates.
Zenz, J. (2005) Agates. Bode-Verlag, Haltern.
16
19
Morocco, the places, the people
and...agates
Holger Quellmalz, Rochlitz, Germany
The colors and structures of agates
from North Africa are unique and easily
recognized. So my friend Christian and
I made a deal with Joachim Pfeiffer to
take us on a two week tour of Morocco.
Joachim recommended that we fly to
Marrakech but fly home from Fez. We
landed in Marrakech, which was cloudy
and a pleasantly warm 25 °C. Ilyass
Pfeiffer, whom we already knew from
shows in Germany, was waiting for us.
Joachim Pfeiffer himself was unable
to accompany us, but he left us in the
competent hands of his son Ilyass.
First we had an opportunity to test
moroccan food. In our hotel restaurant
we ordered our first tagine, an
ubiquitous dish with meat and lots
of vegetables, prepared in clay pots.
Discussing details for the upcoming
days, we spontaneously decided to
visit Ait Ourir, a locality only a couple
kilometers away. We had come for
collecting afterall, and certainly
wanted to take a few kilograms of
rough material home with us!
One immediately feels comfortable
here in Africa, the collector in his
element and the stresses of the distant
homeland quickly forgotten. As at
most of the later localities, here too
weathered basalt was the host rock
for the desirable stones we sought;
one hunts in dried out watercourses
for stream tumbled samples and then
pokes around upstream to find the
primary outcrops.
25
Right from the start a giant nodule
went into my bag, although later
after being sawn, it did not fulfill my
equally gigantic expectations. Many
small amygdules were added too.
With misty weather and comfortable
temperatures, we were well able to fill
our bags and go back happy after three
hours. There was no warm water in the
hotel that evening, but the cold water
was good enough for washing the little
rocks!
As on subsequent days, the evening
brought a respectable downpour of
rain, which luckily helps expose fresh
agates. The first supper was quite
european. We enjoyed a small beer
with our couscous and later shared a
bottle of quite acceptable moroccan
red wine. We were almost the only
guests in the hotel, which cost about
$30 including two meals.
Ait Ourir, like Sidi Rahal, lies in the
Marrakech district, north of the High
Atlas. Several of the locality names
were already familiar to us. In the end
we did not visit the well known Asni, but
we found similar material elsewhere.
Although every collector natually wants
the beautiful colorful pieces from Aouli
and Kerrouchen, the white banded
types have their charm too and come
in amazing variety. From the beginning
we constantly badgered Ilyass to take
us to Al Hama too. He was very polite
about it and never told us a definitive
“No“, although an attentive observer
would have quickly understood that
this would remain a secret spot for the
Pfeiffers. That locality is very small and
the wonderfully colored agates there
provide a not insignificant portion of
the family’s bread and butter.
A visit to the local market the next day
was naturally another high point for
us. Diving into the commercial culture
of a country where the clocks tick at
a different pace. On the one hand
lots of dirt and an unfamilar simplistic
infrastructure, on the other hand the
colors on the vegetable stands and the
relaxed ambiance of the Moroccans.
We used our communal funds for a pile
of basic foods for the trip, including
fruit, vegetables, pita bread, canned
tuna, and of course lots of water.
Along the way we collected a host of
impressions: the butcher slaughtering
the chicken in front of the customer; a
half sheep, with head, hanging from a
hook. Countless stork nests on towers
and poles. And everywhere donkeys as
the main form of transport. Whoever
has something to sell, just offers it
on the sidewalk. Tagine is prepared
everywhere and there are heaps of
pita bread.
Sidi Rahal was our next goal after
shopping, the first more extensive
collecting trip. It is a rather large
region, and hilly, so the hunt for
our little stones was difficult. The
characteristic red crusts were laying
around all over, but not a decent geode
among them. But I stumbled across my
first tortoise, which saved the day for
me! Later the bag filled up more and
more, first in a dried up streambed,
then from old dump material. Farmers
dug adits here for crystal-lined geodes,
and the solid agates used to end up on
the dumps, until it was realized that
these had monetary value too. Now the
agates are sorted by size and packed in
sacks.
Here in Sidi Rahal we quickly noticed
that however one tries to lose oneself
in the landscape, one is never alone.
When you think no one is watching
you, a Moroccan is guaranteed to pop
up behind the next bush! Everyone
is doing something outside. Families
are working together in their fields,
shepherds are watching the sheep,
children are playing outdoors - luckily
still growing up without TV.
Opposite Page: TopAgate from Bou Lili - 11cm wide
BelowAgate from Sidi Rahal - 5.4 cm
Photos by D. Mayer
Current Page: AboveAgate from Sidi Rahal - 8 cm wide
Photo by J. Zenz
Later we visited the landowner and
made our acquaintance with moroccan
hospitality. With tea, flat bread and
olive oil, we squatted in the twilight
and used a weak LED pocket lamp to
look over the geodes he offered us for
sale. There were some neat specimens
with beautiful pseudomorphs, but one
can’t collect everything. Nevertheless,
partly out of gratitude for having let
us collect on his land, I bought one.
A friend of mine bought a whole sack
of agates. Later I kicked myself for
not having done that too. Our self
collected finds were less impressive,
and after sawing them open there
wasn’t a lot worth adding to the
collection. Characteristic for this
locality are the thick red or greenish
white crusts, interesting structures
with spherulites and liesegang rings,
as well as occasional deep violet
chalcedony.
On the third day of our trip we headed
out for the High Atlas. We had planned
to camp in a tent, but that was not to
be, which was a good thing as it later
turned out. I had to make use of my
entire arsenal of clothes: In the evening
we were sitting at about 1,700 meters
elevation in the half open lobby (there
were no doors) and my body’s internal
heater was not capable of keeping up.
All my sweaters were put on at the
same time!
The journey went over the Tizi’n’Tichka
pass (2,260 meters high), past the
first mineral shops, to Agouim. Four
distinct localities are known there,
with the fourth (the so-called “photo
locality“) having yielded beautiful
colored agates, although it was only
a temporary construction-related
outcrop. We visited Agouim I right after
27
our arrival. On climbing on the hill we
stumbled over countless brown and
red jasper shards, and later amygdular
geodes of mixed composition (lots of
chalcedony and moss agate), mainly
before the peak, after which the
basalt is overlain by buntsandstein.
My personal highlight was a roughly
1 hectare patch strewn with well
colored “jasp-agates“ eroded out of
veins. I could not pass this material
by, and by the end of the day I was
overloaded for the first time. Luckily
two of Ilyass’ friends helped me carry
it - 40 kilograms is no trivial weight!
A real highlight was our visit to the socalled “Finger agate locality“, Agouim
II. After several kilometers uphill in
wide hilly terrain, a dry watercourse
yielded giant quartz and agate geodes.
It was a very windy day and it turned out
to be quite strenuous. At some points
up in the hills, one could get scared of
being blown off. As compensation, one
could find after a little hunting some
relatively large geodes still in situ and
work them out, with broken fragments
scattered all about and of course also
some complete specimens of elongated
agates, and I quickly had my first bag
filled. I left the bag out in the field and
forgot to record the position by GPS.
Thanks to my bad sense of orientation,
I had great difficulty finding it again!
But that wouldn’t have been much of
a problem anyway, as vast quantities
of agate were laying all around. One
had to do a strict selection on the
spot, as it would be impossible to carry
everything back. White and grey bands
dominate, including some with fine
contrast, eyes, and a great Wegeler
effect. Pseudomorphs were heaped
up in some spots. We were treated to
beautiful views, with periodic sleet
showers whipping over the crest of the
High Atlas, sucking all the warmth out
of one’s body. But our finds produced
some adrenalin, and in the evening
we returned to the hotel completely
satisfied.
On the third day in the High Atlas we
could feel the changes that are starting
to come to this agate collectors’ mecca:
We found hardly any amygdules at
Agouim III, but instead found the land
owner, who was not at all happy that
the “rich“ foreigners (and anyone who
can afford a foreign vacation must be
rich!) were carting off valuables from
his land - Those stones must be worth
something!
Luckily Ilyass took care of it. After some
discussion it was agreed that we would
visit the owner’s shop and buy some
there. For very little money everyone
got a couple of mineral specimens, and
then we were allowed to do a bit more
collecting in the field. This worked out
well because on a small plateau we
found larger quantities of amygdules
of the Asni type, often highly flattened
and exhibiting a complex inner pattern.
By evening one thing was clear: The
era when one could go around the
country picking up stones anywhere
at will seems to be finally over, and it
won’t get any better.
Departure point for our tour in the
Middle Atlas would be the Pfeiffer’s
country home near Aguelmous,
which meant we’d have to cross the
Tizi’n’Tichka again. We got there in
the evening after a long drive, and
the next day got a tour of the lovely
property and were allowed to view
part of the Pfeiffer’s collection.
After exactly a week already in
Morocco, we started off on the long
awaited several day trip towards Aouli.
In the back of our minds was always
that image of beautifully colorful red
and yellow specimens, and we all had
high hopes for the region, although
of course we realized that everyone
dreams of that and there was no way
we could expect the same density of
finds as at Agouim.
We visited Kerrouchen first. At 1,800
meters elevation, the fields were
half covered with snow which did
not promise the best conditions for
making good finds. Nevertheless a
collector friend quickly found an
amygdular geode on the flanks of a
creek and that inspired a collective
hope. Some material was found on
the fields, apparently overlooked or
abandoned by previous hunters, and in
my case two larger pieces with typical
colors were obtained for the collection.
Agates from Toubkal,
Photos by D. Mayer
The actual better-known Kerrouchen
locality (which is also a field) is still
open for collecting after paying a
fee to the farmer, although it has
been worked already for years by
“professionals“ with heavy equipment,
aided by workers from the local
population. We even heard about a
mobile saw that had been set up there,
and about the destruction - smashing of all the material of little commercial
value. We gave that particular field a
wide berth and searched rather in a
neighboring area that had not been
worked by owners.
The so-called warm water was
mislabelled, but after that things
started looking up. And in cases of
need, Moroccan tea was our saviour.
Unbelievable, the first time we saw
how much sugar goes into that tea! But
one gets used to it, and anyone who
thinks they would be able to make
this highly aromatic drink themselves,
they should try! Tea is part of life in
Morocco, drank everywhere all the
time, and even for tourists it quickly
becomes a fixed routine.
We drove further east, passing Midelt,
the famous mineral dealers’ town and the almost abandoned former
mining village of Aouli. At the foot of
the mountains in this elongated agate
district we eventually reached the hut
of Sahid, a good friend of the Pfeiffers.
To our astonishment, a collector friend
from Germany was sitting in front of
the hut. The world is truly a village!
After brief greetings, we set off for Bou
Lili and left many kilometers of gravel
road in our dust. It is still a mystery
to me how Ilyass managed to find his
way there, especially the drive back
in the evening twilight! But first we
29
steered towards the four distinctive
hills in this mysterious agate district,
in whose creek beds one finds mainly
only agates of the Aouli type.
We found out that the Bou Lili agates,
which alongside the Al Hama ones count
among the latest new discoveries,
come from a limestone deposit of as
yet uncertain origin. They are clearly
identifiable by the distinctive crust on
the outer skin of the amygdules. The
primary source seems to be known
only to the Berbers. Two families put
up their tents in varying locations
here and we hoped to be able to buy
inexpensively priced rough from them.
Unfortunately they had just sold their
entire stocks to buyers from Midelt, so
we were left relatively unsuccessfully
with just the few kilograms of our self
collected material.
In the evening we made our camp in
Sahid’s sleeping room, where a bunch
of mattresses had accumulated over
the years, and the family spoiled us
with a delicious tagine. In their hut we
got really warm for the first time in the
trip, since the fire in the kitchen oven
was constantly lit.
The next day we visited Fullouz I, the
main locality for the Aouli agates. On
a plateau here one finds at best just
broken fragments of the beloved redyellow specimens, but nevertheless
one does not need to go home with an
empty bag. On the way up I discovered
a spot with innumerable geodes sticking
out of the weathered basalt, although
they were all rather fractured.
Dark clouds threatened to ruin our
afternoon and we went back early,
which enabled us to meet the dealer
Khalid, the son of Sahid, and his
wife Giuliana. In their comparatively
luxurious house, very tastefully
arranged by Giuliana, who was born
in Italy, we had a nice conversation
with delicious espresso and baked
goods and then did a bit of plundering
in Khalid’s stone stock. They had only
gotten electricity a few days ago and
were just testing their music system.
Back in the Pfeiffer’s country home
we had another day of rest and
enthusiastically dedicated ourselves
to washing and sorting our finds and
packing them up. It was a pleasant
change, and because of the much
milder climate there we warmed up in
the midday sun and enjoyed the fresh
oranges and pomegranates from the
garden.
We got an early start for the several hour
drive westwards. Rare trees decorated
the highway and the landscape offered
lots to see. We found a few agates with
the typical brown-green crust, eroded
out in the field, but further hunting
was quickly impeded by employees
of the new leaseholder, anxious to
protect his rights, who kept us for a
long time in a sort of state of outdoor
arrest. During the lunch break, a
Moroccan appeared as out of nowhere
with a tray of tea, bread and oil for
the farm employees and we brazenly
joined them. Of course we were
invited to partake, and we attempted
some simple communication. It took a
while, but at last the landlord showed
up in a black A8, with a copy of his
contract for “negotiation“. Meanwhile
the assembled crowd had grown to 16
men and we were made to show the
boss our finds. It turned out that he
himself did business with the stones
collected on his land and exported
rough to America. How things change!
Our self-collected stones evoked merely
a compassionate laugh from him and
we were allowed to keep them. Okay,
I had “accidentally“ let four big geodes
roll out of my bag in the car - but I still
haven’t sawn them and they remain as a
potential surprise until I get to the end
of all my moroccan rough. We would
have gladly augmented our finds by
purchasing some from the landlord, for
his laughable kilo price, but apparently
all his stock had just been shipped out.
I suppose the most beautiful pieces in
my collection from this last locality will
still be the ones I acquired at the Munich
Mineralientage in 2012 from Joachim
Pfeiffer. Zaër Zaiane yielded gorgeous
pseudomorphs and agates with goldcolored goethite sprays, but the quota
of high quality pieces was very sparse.
My thanks to the Pfeiffer family: More
knowledgeable guides would be hard
to imagine. The old Renault-Bus with
its oft replaced motor and seven figure
number on the odometer carried us
unwaveringly to everywhere and back
again.
Addendum: Between the four of us
we brought back almost a ton of raw
material, which caused Joachim Pfeiffer
some unforseen problems crossing the
border. Naturally we brought back way
too much material, but then every
collector does that the first time they
visit Morocco!
Originally Published in Mineralien
Welt issue 4/2014 - Reprinted in
English for the first time here.
Thank you to Alfredo Petrov for
translation services.
Thank you
to Rainer and Kristina Bode for
use of this interesting trip report.
30
Every year for the last 17 years a rather the
town of Lwówek Śląski, in south western
Poland, has been celebrating the region’s
spectacular mineral and mining heritage
with a summer festival that takes over the
center of this historic town.
Lwówek Śląski, in Lower Silesia,
was also known by the German
name of Löwenberg before the
end of World War Two, but the
region became part of Poland
in 1945 after the borders of
Germany were redrawn.
Geologically the region is very
famous. To the east near the regional
capital of Wrocław is the famous
granite quarrying region of Strzegom
where dozens of quarries have provided great
specimens for mineral collectors for well over
100 years. But Lower Silesia is most famous
for the many agate deposits in the area, such
as the world-­famous Płóczki Górne deposit.
The festival takes place in mid­-July and takes over the
whole center of the town surrounding the medieval town
hall building. Inside the 12th century hall a spectacular
themed mineral display is put on each year. Themes have
included Agate, Copper minerals, quartz, amber and the
Minerals of Poland.
Outside the streets are filled with
wooden tables, custom made with local
birch trunks where dealers from Poland
and beyond offer minerals, jewelry,
agates, and all manner of other
handicrafts. A seller of local agates
offers a large pile of local agate
nodules, and has a large rock
saw set up to cut them open
for you on the spot.
The show opens on Friday afternoon and runs until Sunday
afternoon, but that is not the only outdoor part of the
festival. A massive stage is erected next to the Town Hall
at one end of the main street, and throughout the day
it is used for local folk music, presentations by the town
and a series of competitions including strong man, and
who can cut the (fake) agate boulder the fastest.
On Friday a huge parade marches through
the town with everyone from the local
police, local brass band, hospital staff,
classic motorbike enthusiasts and even,
from time to time, mindat.org members
represented.
On Saturday and Sunday evenings the town
center is packed for a music concert with
local, national and international artists.
Sunday evening’s event is by far the most
important with the headline group(s) performing
in front of tens of thousands of people.
After the end of the concert the festival draws to a close
with an incredible laser show (previous years had firework
displays but they became concerned that the large display
might potentially damage the historic buildings, so it was
replaced).
Since my first visit in 2010 to the festival, I have
been back three more times. In 2011 we held our
first mindat.org Conference in conjunction with the
event. And for the last two years we have held mini­
mindat gatherings during the show as a chance for
mindat.org members to get together and enjoy the
event. There are always something exciting going
on, with no end to food, drink, mineral collecting
and great company. Now that this tradition has
been firmly established I am delighted to say that
mindat.org will be having a regular attendance
at this event.
If you’re interested in coming to this event
in 2015 then please get in contact with us
(contact information near the front of this
magazine) or check details on mindat.org
later this year.
34
Agate and Associated Minerals from the
Creede District, Mineral County, Colorado USA
Philip Persson - Philip.m.persson@gmail.com
A notable example of a distinctive
occurrence of agate with other
collectible minerals is the Creede
District in Mineral County, Colorado
USA. This world-class epithermal
silver district has produced over
2.3 million kg. of silver (Ag), in
addition to significant lead (Pb),
zinc (Zn), copper (Cu), and gold
(Au) (Robinson & Norman 1984).
The silver deposits at Creede
are a classic example of an
epithermal vein system in which
relatively shallow hydrothermal
systems (in this case related to
mid-Tertiary age volcanism and
caldera collapse) circulated metalrich fluids through fault conduits,
allowing the precipitation of
distinctive, often banded mineral
assemblages which host economic
metal concentrations (Rosemeyer
2010).
The silver veins of Creede were
first discovered in 1889 by itinerant
prospector
and
adventurer
Nicholas Creede, making it one of
Colorado’s last major mining camps
to be founded (Voynick 2006).
Creede’s initial discovery, which
he named the Holy Moses Vein, was
rich in Ag, Pb and Zn, and led to
the discovery of numerous nearby
35
veins which typically ranged from
1-5 m. wide and followed steeplydipping faults cutting the thick
sequence of volcanic rocks related
to the collapse of the huge Creede
caldera during the lower Miocene
period (Wetlaufer et Al. 1979).
These veins, which are related to
what geologist’s call a keystone
graben (imagine a ‘keystone’
block in an arch developing along
a weak tension point with two
parallel inward-sloping cracks),
were fabulously rich in silver,
with a rhythmically-banded core
averaging several hundred ounces
of silver per ton or ore, and a
lower-grade halo of Zn-Pb-Cu
mineralization extending up to
15 meters outward from the vein
(Voynick 2006). The largest vein
system in the district, the Amethyst
vein, was first mined in 1892, and
brought the nascent district’s
silver production from ~380,000
ounces a year to over 2.4 million
ounces! (Voynick, 2006) In addition
to bringing great wealth to Creede
that would last for nearly the
next 100 years, the Amethyst vein
system would also become the type
locality of sorts for a fascinating
variety of cryptocrystalline quartz
known as ‘sowbelly agate.’
The Creede District is well known
today for a type of agate known
locally as ‘sowbelly agate’ due to
its distinctive bacon-like rhythmic
banding made up of alternating
layers
of
pale
gray-white
chalcedony and vibrant purple
amethyst. Indeed, in deposits
such as the Amethyst vein system,
amethystine quartz agate was the
primary gangue mineral associated
with the ore! In veins such as the
Amethyst, the mineralogy was
strongly zoned both laterally and
with depth. The vein consisted
of a core exhibiting a geode-like
concentric structure as much as 5
meters wide. The outer part of this
core consisted of dark, fine-grained
chalcedony and quartz rich in Ag
sulfides and sulfosalt species such
as acanthite and argentiforous
galena, which was followed by a
layer of finely-banded ‘sowbelly’
agate (Voynick 2006). This is turn
was followed by another layer of
mineralized quartz, sometimes
containing native silver crystals,
and then a layer of violet amethyst,
often showing euhedral crystal
projecting into the enclosing
agate; an especially aesthetic
association. Associated with the
amethyst and agate of the vein
core were excellent crystals of
gemmy honey-brown and green
sphalerite along with galena,
acanthite, native silver, and rarely
species such as proustite and
Stephanite (Eckel 1997).
Sowbelly Agate slab, Creede District, Mineral County, Colorado
(field of view ~9 cm. across)
[Photo courtesy of the Colorado Geological Survey]
36
Crystallized sphalerite from the
Commodore mine is amongst
the best in the U.S, occurring
as sharp, lustrous crystals from
1 to 10 cm. showing excellent
color when backlit. Specimens of
sphalerite, sometimes occurring
with fine crystals of chalcopyrite,
galena and pyrite, associated with
deep purple amethyst crystals
are particularly prized, and were
found on multiple levels of the
OH and P veins.
Sowbelly agate was common in
many mines along the Amethyst
fault system, including the Last
Chance, Amethyst, Bachelor, and
Commodore mines. Thousands of
slabs have been cut out of this
material, which often exhibits
fine repeating band structure
and euhedral amethyst crystals
projecting into chalcedony layers,
a hallmark of many high-grade
epithermal Ag-Au vein deposits.
Map by
Brandy
Zzyzx
37
Some of these mines, such as the
Commodore, were mined until
relatively recently (late 1970’s),
and produced literally thousands
of pounds of fine agate specimens
in
association
with
wellcrystallized amethyst, barite,
and sulfides. While much of the
sowbelly agate in these veins was
mineralized as explained above,
the outer layers of agate and
chalcedonic quartz were often
barren of Ag mineralization, and
thus ended up on the huge dumps
which dot many of the canyon
walls along East and West Willow
Creek’s. Sowbelly agate can
still be collected in the Creede
District. The author recommends
the Last Chance Mine, which
hosts a free museum and also a
fee collecting site in the summer
months, where for a modest
$2.00/pound, one can fill their
bucket with beautiful sowbelly
agate specimens.
In the Amethyst and OH vein
systems,
mineralization
is
generally finer-grained and also
distributed across a wider area
than other Creede deposits
(Robinson & Norman 1984). Normal
faulting created open spaces in
which circulating, boiling solutions
containing abundant silica as well
as metals such as Ag and Zn/Pb
dissolved as chloride complex
could crystallize in a sequential
fashion outward from he center
of the vein (Robinson & Norman
1984). Agate in these veins occurs
in a variety of forms, including
finely-divided ‘sowbelly’ agate,
more massive crystalline amethyst
alternating with white chalcedony
layers, and vuggy, brecciated
agate which sometimes appears
to surround hollow casts of
dissolved rhodochrosite, quartz,
or barite. The occurrence of
pale-pink rhodochrosite, which is
paragentically early in these veins,
with silver minerals and agate is
particularly interesting (Robinson
& Norman 1984).
Commonly associated with the
‘sowbelly’ agate are fine-grained
layers of the silver sulfide mineral
acanthite,
and
occasionally
spectacular ‘herringbone’ crystals
of native silver projecting into
the amethystine quartz layers.
Crystals of sulfide species such
as sphalerite and galena, which
are paragenetically late in these
assemblages,
sometimes
are
implanted on small euhedral
amethyst crystals forming the
outer edge of an agate layer,
making for very handsome
specimens. Crystals of white
barite are also associated with
agate in some veins such as the
Bulldog Mountain. Because the
mineral-rich
solutions
which
formed the Creede veins were
circulating in a conveyor-belt like
manner through high-angle fault
systems, they were cooled and reheated on a relatively short time
scale, as well as “recharged” by
the influence of meteoric water
from the surface. This allowed
the ‘sowbelly’ agate to develop a
fine structure indicative on many
periods of crystallization, as well
as the close association with orestage minerals like native silver.
Probably the most spectacular
specimens of native silver from
Creede were found relatively
late in this district’s history,
during the first few years of
operation of the Bulldog Mine,
discovered during the mid-1960’s
by Homestake Mining Corporation
and mined until 1985 (Plumlee &
Whitehouse-Veaux 1994). While
more commonly associated with
barite, some of these specimens
were also found with silver
inter-layered with agate and
cryptocrystalline quartz, making
very attractive specimens when
slabbed.
38
References
Native Silver
in ‘Sowbelly’
agate: Creede
District,
Mineral County,
Colorado USA
(field
of
view ~9 cm.
across)
(Photo
©
Ron
Wolf,
CSM Geology
M u s e u m
Collection)
In their 1994 study, Plumlee &
Whitehouse-Veaux identified 6 periods
of mineralization in the Bulldog vein
system, stages A-F, with native silver
occurring primarily in stages B and
F. Most silver is in massive white
barite, which shows strong banding
due to re-circulating hydrothermal
fluids traveling vertically through
the fault system and depositing
alternating layers of silver, barite,
and acanthite. The association of
crystalline barite and relatively lowtemperature silver sulfide species
with agate is interesting in these
assemblages in that it is indicative of
the highly fluctuating temperature
and fluid conditions in these veins.
During the early years of the Bulldog
mine, specimens of nearly pure
native silver up to 50+ kg. were
sometimes found, as well as beautiful
specimens of delicate ‘nests’ of wire
silver implanted on barite or agate.
39
While the boom days of Creede
are long past and it is now a fairly
quiet former mining town with a
short summer tourist season where
visitors flock to the historical
theater, shops and restaurants of
downtown and to see the mine
ruins clinging to thousand foot
canyon walls up Willow Creek,
there is some hope that silver
mining will resume. Helca Mining
and its subsidiary Rio Grande Silver Inc
have been actively exploring the
Bulldog and Equity mines for the
past ~5 years, and if silver prices
and drill results are favorable, will
likely resume mining in Creede
in the coming years. Beautiful
specimens of agate and associated
minerals will almost certainly be
found if mining resumes, and the
little town of Creede on the edge
of the mighty San Juan Mountains
will once again be a silver city.
1.) Rosemeyer, Tom “Creede: The
Last Wild West Silver Mining Camp in
Colorado,” Rocks and Minerals 85, no.
5 (2010): 396-413.
2.) William H. Emmons and Esper S,
Larsen, “Geology and Ore Deposits
of the Creede District, Colorado,” U.
S. Geological Survey, Bulletin 719,
(Washington: Government Printing
Office, 1923).
3.) Richard W. Robinson and David I.
Norman Mineralogy and fluid inclusion
study of the southern Amethyst vein
system, Creede mining district,
Colorado Economic Geology and the
Bulletin of the Society of Economic
Geologists(May 1984), 79(3):439-447
4.) Geoffrey S. Plumlee and Pamela Heald
Whitehouse-Veaux Mineralogy, paragenesis,
and mineral zoning of the Bulldog Mountain
vein system, Creede District, Economic
Geology and the Bulletin of the Society
of Economic Geologists(December 1994),
89(8):1883-1905
5.) Voynick, Steven, “Another Chance for
the Last Chance Mine”, Colorado Central
Magazine, July 2006.
6.) Wetlaufer, P.H, Bethke, P.M, & Barton,
P.B: “The Creede Ag-Pb-Zn-Cu-Au District,
San Juan Mountains, Colorado: A Fossil
Geothermal System” pp. 159-163, Papers on
Mineral Deposits of Western North America:
5th IAGOD Symposium Proceedings.
7.) Eckel, E.B., Cobbin R.R, Mosburg S.K.
‘Minerals of Colorado’, 1997, Fulcrum
Publishing, Golden, Colorado
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