Newsletter Volume 34 No. 3 Spring 2014

NORF
LK MINERAL & LAPIDARY SOCIETY
STONE CHAT
Vol.34 No.3
Spring 2014
WORKSHOPS
Two lapidary workshop days have been arranged for members, both
experienced or beginners, as follows
Tues 29 April at Martin’s home at Lyng (Richmond Place)
Tues 15 July at Chis’s home at Gorleston
If you are interested, contact the hosts. Transport may be possible.
Our Winter issue was produced in a bit of a rush as I had several health issues to
address. I was therefore unable to proof read part of the material – hence the
apology you will find in these pages. Sorry Georgie and to you all.
As Martin was recovering from his knee op , our scheduled talk due in February
had to be postponed. It was replaced by one of our ever-popular Micro Nights. For
those disappointed, all being well the Laurion event should be in April.
March once again brings us to our AGM, and we urge all who can to be there and
support your committee. We do not expect any anything major to happen and it
should be over in double quick time. It will be followed by a talk on Gunnerside
Gill in the North Yorkshire Dales.
At the time of writing (late January) Club officials are going down like flies. Roy
has had a fall and broken his right arm in two places, Martin is having a knee joint
replacement and I am having an angioplasty procedure in a few weeks. Perhaps we
should open a branch at the NNUH!
COVER PICTURE:
Blue John bowl on display in Castleton Visitor Centre
1
th
50 MUNICH SHOW
th
October 25 - 28 2013
© Reproduced from SMLS Newsletter No. 247 by kind permission
th
This was my first visit to the Munich Show, and I thought that the 50 Anniversary
Show might be a good one to attend – I was not mistaken. I joined the mixed group
from SMLS, Norfolk, BMS / Russell Society, staying at the Hotel Accolo, a short
walk from the railway station in Feldkirchen, and only a ten minute bus ride away
from the Messe Munich Showground.
The Show opened to the trade on Friday morning and our host, Manfred Seitz, had
kindly arranged to purchase some discounted tickets for us for 3 days at the Show.
Figure. 1 captures Manfred (blue shirt looking towards the camera) on the Mineral
Friends of Munich stand surrounded by minerals for sale and a batch of
microscopes at the back for the micromount enthusiasts. This was our base and
meeting point throughout the 3 days. Figure 2 shows our party heading for the
Messe in good time for the opening at 09.00am – that’s Trevor Devon striding out
in the lead (going pretty well, considering that he’s wearing John Pearce’s shoes,
which were a size too big – see later!)
The Show entrance was like the starting gate at the Grand National – everyone
jockeying for position and trying to make sure they were strategically placed to be
first through the turnstiles, heading for their particular first “target”.
I made a beeline for the special exhibit on gold, where some of the finest and
largest specimens ever found had been assembled from museum and private
collections across the world. I counted over 300 individual gold specimens ranging
from exquisite single crystals from Venezuela, to the astounding Ausrox nugget
discovered by a prospector using a metal detector in 2010 and weighing-in at
23.26kg (748 Troy ounces). There were a number of truly outstanding specimens –
both for sheer size and aesthetic quality. The largest (and presumably most
valuable) items were exhibited in glass-fronted safes, which nicely augmented the
feel of being in a bank vault. Perhaps the most famous specimen is the so-called
“Dragon” (Fig. 3), Colorado Quartz Mine, Mariposa County, California, from the
collection of the Houston Museum of Natural Science.
(http://en.wikipedia.org/wiki/Houston_Museum_of_Natural_Science)
The show occupied four halls (somewhat like the NEC in Birmingham), and these
were Mineralworld, Gemworld, Stoneworld and Fossilworld respectively. The
2
bulk of dealers and material of interest to myself and most mineral collectors was
in Mineralworld – hall A5 and Fossilworld - hall A6 (Figure 4 shows an overview
of hall A6) and this is where I spent most of my time. I did however do a circuit of
the other two halls, and there were certainly interesting things to see and do in
those areas as well.
There is an excellent, and well-illustrated on-line report of the show by Stefan
Schorn (one of our local hosts in Munich), including a nice photo of our group at
the International Social evening.
http://www.mineralienatlas.de/lexikon/index.php/Events/Mineralientage%20
M%FCnchen%202013%20-%20The%20Munich%20Show
Fig. 1 Manfred on the
Mineral Friends of
Munich stand
Fig, 2 Trevor leads the
way to the Show
3
Photos were all Roy Starkey’s, except figures 4, 8 and 9 which were taken by
Jolyon and Katya Ralph.
Fig. 3 The Dragon gold
specimen
I’ll start by mentioning a few
of the “outlying “areas and
displays, and come back to
minerals at the end.
This
year’s
special
exhibition in Stoneworld
was called Set in Gold –
Precious
Stones
within
Christianity, and featured a
selection
of
fantastic
ecclesiastical
treasures,
together
with
some
interpretative
background
information which made for
an informative and aesthetic
exhibit.
I was struck by the stand of
the
German
Blind
Association – titled Steine
Begreifen
–
literally
“grasping stones”, situated
adjacent to the Treffpunkt
Forum. Here, visitors were invited to examine six specimens (in the dark) by touch
and feel alone, and then to re-emerge into a display area where twenty specimens
were laid out with labels. The task was to correctly match the specimens “seen” in
the dark with the correct samples in daylight. For a reasonably competent
mineralogist / geologist this was not difficult, and in fact I correctly identified
them all in the darkened booth before re-emerging, but it did make one think about
what the world of a partially sighted or blind person is like. I thought this was a
really innovative idea, and maybe something SMLS might try at the Sussex Show
in association with RNIB.
4
The gem and jewellery hall had the usual selection of countless thousands of beads
and bangles, but also some really high class gemstones and jewellery (e,g. these
superb carvings from Brazil – Fig. 5). I particularly liked a selection of tanzanite
jewellery at the CHQ GmbH booth, but was accosted by one of the stand officials
who snapped “Nicht photos!” – which I guess can be understood in most
languages.
Fig 4 Overview of Hall A6
Sadly this seems to be
becoming more and
more of an issue and
is I think regrettable. I
do not understand
why people who are,
after all, trying to
promote their wares
and get people to buy
them, should feel
somehow threatened
Fig, 5 Superb mineral carvings on
the stand of Peter Muller, Brazil
5
by enthusiasts wanting to take home an image to share with their friends. It is often
said that there is no such thing as “bad publicity” and I would have thought in the
case of selling minerals and gems that was certainly the case. I met with the same
reaction on one or two mineral dealers’ stands when I asked for permission to take
a photo, but in the main, there were plenty of “happy snappers”, and in fact at least
one collector was streaming live video of the show back to Japan from his iPAD!
The fossil display picked up on the theme of “golden discoveries in
palaeontology”, and showcased some particularly significant fossils which have
contributed to our understanding of evolution. Figure 6 captures a young visitor
admiring a Miocene Mastodon skeleton (Gomphotherium) at the Show.
Fig. 6 Young visitor checks out a Mastodon
6
Back in the Mineralworld hall there was a second special exhibition called
Treasury Carinthia featuring top-class finds from the Alps, and an opportunity to
chip out your own garnet crystals from blocks of schist – great fun! The central
pavilion was surrounded by a range of individual dealer stands and exhibits,
including that of brothers Gerhard und Hannes Hofer (Fig. 7), strahlers who offer
videos of their exploits. There are some great photos and some insight to their
activities on their website here (http://www.alpinmineralien.com/). The efforts to
which these guys go in the quest for fine alpine cleft minerals is truly amazing.
Fig. 7 Alpine quartz
display Fig, 8 Crystal
Classics – Bavarian
style
In one of the outdoor areas adjacent to the
Show halls was a popular exhibit of
reproduction (plastic) dinosaur models.
These were extremely life-like, and had
been put on show by Wolter Design. Small
ones start from about 2000 Euros, and
range upwards to 10,000 Euros and beyond
for larger ones. If you fancy one for the
garden
(Nick?)
–
see
http://wolterdesign.de/index.php?home
7
The main mineral hall was almost overwhelming. As is the case with Tucson,
Sainte Marie and other major shows, there is almost too much to look at, and it is
easy to miss things. The only solution seems to be to make serial circuits of the
stands most likely to be of interest. The slice of wooden mine timber partially
replaced with copper (Fig. 9) certainly caught my attention.
Fig. 9 Slice of wooden mine
timber partially replaced
I collect only British minerals, and in the main, these were in short supply (with
the obvious exception of Crystal Classics, who changed into Bavarian gear at the
end of day 1 – Fig. 8 captures Diane, Elizabeth, David and Ian in costume. There
were a few nice pieces to be seen on the stands of Wendell Minerals
(http://www.wendel-minerals.com/default.aspx) and the Arkenstone - Rob
Lavinsky
(http://www.irocks.com/),
although the prices of course were
not for the faint-hearted. I will
mention in passing that my vote
for “case of the show” goes to the
end case on the outer wall of Rob
Lavinsky’s booth (Fig. 10)– it
was simply outstanding, fantastic
minerals,
properly
labelled,
beautifully presented and not
crowded. If you had to ask the
price, you couldn’t afford it!
Fig 10. Rob Lavinsky’s
choice cabinet with copper
from Cyprus
8
In addition to the dinosaur models outdoors, there were a good number of activities
aimed at encouraging younger visitors. These included the ever-popular goldpanning, silver-smithing, digging / screening (in sand pits) for gemstones, carving
talc, developing fossils using dental tools, knapping flints to manufacture axes and
arrowheads, and undoubtedly the most popular of all (with youngsters and adults
alike) splitting finely bedded like-mudstones from the Green River Formation of
Wyoming in search of superbly preserved fossil fish. The Green River Formation
of southwest Wyoming is famous for two distinct zones of very fine-grained lime
muds, noted for preserving a variety of complete and detailed fossils. These layers
are an Eocene Lagerstätte, a rare place where conditions were right for a rich
accumulation of undisturbed fossils. The most productive zone—called the split
fish layer—consists of a series of laminated or varved lime muds about 6 ft (1.8 m)
thick, which contains abundant fish and other fossils. These are easily split along
the layers to reveal the fossils. This thin zone represents some 4000 years of
deposition. The accompanying photo (Fig.11) shows whole families happily
chipping away – now “that’s entertainment!”
Fig. 11 Getting down and dirty extracting fossil fish
9
There are plenty of attractions in Munich apart from the Show.
On the Thursday afternoon before the Show I stopped off in central Munich with
Michael
Doel
to
visit
the
Museum
Reich
der
Kristalle
(http://inzumi.com/en/travel/point-ofinterest/d_id/Munich/c_id/Sightseeing/p_id/Mineralogical-Collection).
The
museum is part of the Mineralogical State Collection in Munich and its origin was
the valuable collection of the Dukes of Leuchtenberg. The permanent exhibition
presents around 700 mineral specimens and gemstones. There are also exhibits
explaining how minerals are formed, various applications as raw materials, and
something about their physical and chemical properties.
We had been recommended to visit an open air market on the Sunday morning and
after two full days at the Show, seven of us did this led by Trevor Devon. Not only
did Trevor navigate the group across Munich on the bus and railway networks, but
he ensured that we joined the crowds of visitors in Marienplatz just before the bells
struck 12 o’clock midday, gazing up at the tower in wonder as the highly coloured
figures rotate as they
record some of the history
of Munich (Fig 12).
On the Monday most of
the group gravitated to the
airport on their way home,
but four of the group went
into the centre of Munich
to admire its superb
architecture,
the
art
galleries and the Science
museum before taking a
later flight.
Fig. 12 Spectacle in the
tower at noon in Marienplatz
10
The Editor [of the Sussex Newsletter]set a very tight space limit for this review,
which could obviously be expanded greatly, so I’d better finish, but before I do,
back to those shoes ……
John Pearce had taken a pair of trainers to Munich so on the first day of the Show
he decided to wear the trainers to give his shoes (size 12/13) time to breathe. He
was a little surprised when he returned to the hotel room and found that his shoes
were nowhere to be seen. He thought that maybe the hotel management might have
decided they needed a clean, and other members of the group helpfully suggested
he should look under the beds or even in the mini-bar. John was sharing a room
with Trevor Devon and it was only when they both returned from a Social evening
organised by the local Micromount Society that John realised what had happened.
Trevor (foot size 10/11) had worn John’s shoes all day without realising his
mistake, although he did complain of some discomfort in his legs. The moral of the
story? Never share a room with anyone with feet of comparable size.
Finally, those of you who are reading this as the “electronic” PDF version will be
able to make use of the various hyperlinks embedded in the text. This is one of the
very real benefits of “electronic newsletters” – effortless access to background
reading and material. For those of you working through the hard-copy (emphasis
on the word HARD) – just give Colin Lansdell* a ring, or drop him an email, and
he’ll get you fixed up with an electronic version – just like that!
Many thanks to Richard Belson for organising this most interesting and successful
trip, which went like clockwork; also Manfred and Regina Steitz for looking after
us and inviting us to their International Social evening, where 70 people sat down
for a meal and provided a chance to make new contacts.
Roy Starkey
* This has been – changed from “John Pearce” the editor of the Sussex Newsletter
I hope it works for us too.
CL
11
Haltcliffe copper smelter and associated leat immediately
east of High Wath Ford have been scheduled as an Ancient
Monument
Date first scheduled: 25-Jun-2001
Reasons for Designation
Copper was extracted in Britain intermittently from the Early Bronze Age (about
2000 BC) until the early 20th century, after when the industry was confined to byproduct production and small scale reworkings of mines and dumps. There is very
limited evidence for copper mining before the 15th and 16th centuries, and most
known sites are of later date, principally of the industry's 18th and 19th century
peak after it had been revitalised by developments in smelting technology. In the
18th and early 19th centuries, as perhaps it had also been in prehistory, British
production was important on a European scale.
The smelting of copper to produce pure metal was a complex process involving
prolonged and repeated roasting (heating without melting) before the roasted ore
was broken up and melted to form a matte (a solid mass of copper and iron
sulphides). This was followed by further roastings and remelting to refine the
metal. Due to the multiple processes, the consumption of fuel was great, and
smelting has typically been located close to fuel sources rather than to the mines.
The use of the reverbatory furnace was developed in the late 17th century and
dominated copper smelting from that date. Early reverbatory furnaces consisted
simply of a barn-like building containing the furnaces, with chimneys projecting
from the outer wall. The late 18th and 19th century smelt mills were often larger
complexes containing several smelting furnaces and roasting furnaces for
preparing the ore, together with systems of flues, condensors and chimneys for
pollution control and the recovery of sulphur.
Despite demolition of all buildings, the site of Haltcliffe copper smelter and its
associated leat, wheelpit, slag debris, spoil heaps and dressing waste survives
reasonably well. The monument is a rare example of a 19th century copper smelter
in north west England, and together with buried remains of the smelting house and
associated features it also retains abundant copper processing residues which
contain significant technological information.
12
The monument includes the earthworks and buried remains of Haltcliffe 19th
century copper smelter and an associated leat east of High Wath Ford. It is located
on the southern side of Carrock Beck and includes a leat, wheelpit, slag debris,
spoil heaps, dressing waste and the buried remains of the smelting house. The
precise dates when the smelter was built and when it ceased working are unknown;
it is known to have been in use in 1866, however, it was not shown on maps of
1900 which suggest that it had been demolished by this date. Recent analysis of
minerals found here indicate that the smelter served both the nearby Carrock End
and Carrock Fell mines.
A leat, which provided water power for the reprocessing of slags, survives as a
narrow channel commencing a short distance downstream of High Wath Ford.
This leat runs east for approximately 150m before terminating immediately above
the narrow flood plain of Carrock Beck. At this point a gorse-filled hollow is
considered to represent a wheelpit which housed the waterwheel used to power
machinery at the smelter. On the beck's flood plain there are numerous features
including traces of a short section of cobbled road or floor, areas of slag debris
from the smelting process, and remains of a stone wall dividing two large areas of
slag. A number of mounds and hollows at the southern edge of the flood plain
represent a combination of spoil heaps and dumps of brick and slate from
demolished buildings. Examination of the slag debris reveals that two of the areas
of debris are heavily mineralised whilst two other areas show little, if any,
mineralisation, indicating that varied smelting processes have taken place here.
Book Reference - Author: Savage,K. - Title: Some Notes on the Haltcliffe Smelter
National Grid Reference: NY
35116 35049
The above has been extracted
from a document, on the
Internet, by English Heritage.
No. 1019957
Thanks to Martin Stolworthy
for providing this item.
The internet lists 23 minerals
from this site including this
Serpierite
13
Thunder Eggs
via Strata Gem, November 2009 via The Rockhound January 2010
Thunder eggs are lithic structures – rocks not minerals. Like other structures, such
as nodules and geodes, they are formed, and found, in igneous material, rhyolites,
welded tuffs or perlitic rocks. They have a knobby rind of drab, siliceous rock,
often with a characteristic ribbed pattern. The inside of the outer shell has a
relatively thin transitional lining of iron or manganese compound and/or opal or
chalcedony. The centre cavity is filled with opal, chalcedony and/or agate, and it is
this solid centre that distinguishes the thunder egg from the geode.
In 1892, gem authorities from Tiffany’s gathered $20,000 worth of opal-filled eggs
from a deposit in Oregon and the Thunder eggs have been the most popular “rock”
in Oregon since. They were designated Oregon’s official state rock by the Oregon
Legislature in 1965, the choice being supported by a 2-to-l vote by members of the
mineral and gem clubs of Oregon and by the patrons of the Oregon Museum of
Science and Industry (OMSI). Rockhounds have been collecting the eggs from
Crook, Jefferson, Malheur, Wasco, and Wheeler Counties.
Thunder eggs were similar to geodes at some point in their creation, once hollow
and formed in a subterranean void, such as volcanic gas pocket. The processes of
formation are still argued, some holding that the characteristic and unique internal
pattern of typical eggs is due to expansion and rupture of rock by gases and others
that it is due to desiccation (drying) of a colloid or gel. Whatever the process, once
the egg is formed, further development is extremely variable in the amount of time
needed to complete the egg, in the amount of infilling, and in the record of
geologic events. Some eggs contain brecciated rock fragments, while others show
faulting, offset, and healing. In some areas, it is common to find the characteristic
chalcedony core weathered out of its shell.
When sawed open and polished they may
reveal the most exquisite and colourful
designs ranging from five-pointed stars to
miniature ocean scapes or gardens.
Some of the finest and most famous
thunder eggs come from deposits in the
Richardson’s Rock Ranch in Oregon
[example right] where the eggs dug out of
a fragile perlite layer under a coal bearing
strata. The eggs don’t get much bigger
than baseball size and many of the best
14
ones are no more than the size of a walnut but their colours and the patterns can’t
be beat. The thunder egg agates of Succor Creek Oregon look like warty rocks or
stony dirty snowballs when dug, but when cut and polished their distinctive agate
is fabulous, clear and bluish grey with
dark dendrites or white agate bands in a
matrix flecked like granite and coloured
from purple to white [see right].
Thunder eggs are sometimes found with
fortification banding, horizontal layering,
with any open area filled with clear
chalcedony or inward-pointing quartz
crystals, with some layers composed of a
fibrous cristobalite (lussatite) or a partial
botryoidal filling of an opal form of low
cristobalite, opal fluorescent because of a
low content of uranium salts. One
collecting site in Oregon has eggs filled
with carnelian; another, the filling may
contain cinnabar, causing colours pastel to
intense red, or filled with pastel jaspers. If
you could cross an Oregon thunder egg
with an agate from Northern Mexico, you
would probably get something like the Deming Agate from the Baker Ranch in
New Mexico [below].
Formed hundreds of miles
from the volcanic activity that
created the numerous Eastern
Oregon thunder egg deposits,
their eggs were still created by
the same geologic forces.
However, the eggs are sought
for the fine fortification agate
in brilliant colours that rival
the agates of Lagunas and
Moctezumas, typically red
with black, grey, blue and
(rarely) yellow. They are rarely fractured and often have hollow centres with either
a druzy, cinnamon centre, or well formed clear quartz points, or with long crystal
stalactites that span the hollow centre of the stone, or one of these crystal
formations yields a fine white feathery plume through the centre of the stalactite.
15
BLUE JOHN
You may have heard that a ‘lost’ vein of Blue John has been rediscovered
atTreak Cliff Cavern at Castleton.
Briefly, an old time miner. John Royse, discovered a deposit of this fluorite in
1945 but died before he was able to pass the location on to the, then, new owners
of the cavern. It has now been found hidden under an old piece of carpet and is
expected to last for at least a decade.(the vein not the carpet)
Well, I don’t believe we have covered Blue John in detail before, so here goes…..
Derbyshire Blue John (also known as Derbyshire Spar, or simply Blue John) is
a semi-precious mineral, a form of fluorite with bands of a purple-blue or
yellowish colour. In the UK it is found only at Blue John Cavern and Treak Cliff
Cavern at Castleton in D
erbyshire. During the
19th century, it was
mined for its ornamental
value,
and
mining
continues on a small
scale.
Vein at Treak
Cliff Mine
16
Etymology
The most common explanation for the name is that it derives from the French bleujaune, meaning 'blue-yellow'. The story goes that Blue John was exported
to France where is was used by ormolu workers during the reign of Louis
XVI (1774–91). However, there is no archival record of any Blue John being
exported to France,[1]:7 and the early ormolu ornaments which use Blue John were
being manufactured by Matthew Boulton of Birmingham in the 1760s.
An alternative origin of the name derives from an old miners' name for
the zinc ore sphalerite which they called "Black Jack". Thus the unique blue stone
mined in these caverns could easily have become known as "Blue John".[1]:7
Another derivation comes from the Cornish miners who began working the
Derbyshire lead mines in the 1740s. The name Blue John is used for several rocks
in Cornwall,
including
fluorspars,
and
derives
from
the Cornish
language word bleujenn, in Old Cornish blodon, a flower, bloom or blossom.[2]
17
Geology
In the United Kingdom, the blue, banded, fluorite known as Blue John is
found only under the triangular hill known as Treak Cliff, just outside the
town ofCastleton.[1]:20 Today the veins are mined only in Blue John
Cavern and the nearby Treak Cliff Cavern, although the abandoned Old Tor
Mine on the north side of Winnats Pass was also, at one time, a source for
the mineral.[1]:36
The entrance to Blue John Cavern
Mineralogy
The mineral veins of the Peak District were formed during the
late Carboniferous and early Permian times, when the limestones were at a
depth of 3 kilometres (1.9 mi).[1]:13 The minerals were deposited in veins by
layers of crystals precipitating from hot fluids coating the walls of fractures,
caves, and other cavities.[1]:17 Petrological analysis has shown that the Blue
John, like fluorite elsewhere in the Peak District, crystallised from a
highly saline fluid at temperatures of 90–120°C or perhaps a little
higher.[1]:25
Despite much investigation, the origin of the blue colour of Blue John
remains uncertain. Microscopic analysis has failed to find any impurities
such asPotassium permanganate or hydrocarbons which could produce a
18
purple-blue colour. It is now thought that the colour may be a physical
phenomenon due to crystal lattice dislocation. If the regular arrangement of
atoms in the fluorite molecules are disturbed or dislocated, then this may
yield the blue colour in Blue John.[1]:27 The cause of these dislocations is
unknown, but one possibility is that it is due to colloidal calcium, i.e. excess
of calcium atoms needed to form fluorite.[1]:28 Blue John can be
decolourised by heating it in an oven for a few hours, a phenomenon
apparently caused by the heat realigning the lattice dislocations removing
the colour. Irradiating the discoloured Blue John in an atomic reactor can
bring the colour back.[1]:29
Similar rocks elsewhere
Blue, unbanded, fluorite occurs in many localities around the world. Within
the UK, blue fluorspars are also found in County Durham,
especiallyWeardale.[1]:39 Elsewhere, blue fluorspar is known in
the Ardennes region of Belgium; the Cave-in-Rock area of Illinois in
the USA;[1]:39and at various localities in Mexico and China.[1]:40
Blue-banded fluorite is very rare. An ornamental mineral known to the
Romans as murrhine may have been a fluorspar similar to Blue John.
Recently discovered deposits in China have produced fluorite with
colouring and banding similar to the classic Blue John stone.[3]
History
It is sometimes said that Blue John of Derbyshire was discovered by the
Romans.[4] However the earliest source of this story is William Adam's
1843 book Gem of the Peak. It seems likely that Adam was attempting to
add some mystique to the Derbyshire Blue John.[1]:53 Although the Romans
did mine lead in Derbyshire, there is no evidence that they encountered the
Blue John veins.[1]:52
The earliest reference to the mineral "Blue John" occurs in a letter dated
1766 noting a lease from Lady Mazarine, which states that "Lady Mazarine
let ye Blue John, Castleton".[1]:59 The next reference occurs in a 1768 letter
by the industrialist Matthew Boulton who attempted to purchase or lease
the mines so that he could mine the Blue John to create decorative vases
(ormolu).[1]:64 It is clear that by this date the mining of Blue John had been
going on for several years. The earliest dated decorative applications of
Blue John in Britain are those in use as fireplace panels. The bridal suite of
the
Friary
Hotel
in Derby has
a
Blue
19
John plaque dated to around 1760.[1]:69 About the same time, fireplaces with
Blue John panels were designed by neoclassical architect and interior
designer Robert Adam, and installed at Kedleston Hall near Derby.[1]:69
Later Output
By the 19th century Blue John was being fashioned into a wide variety of
ornamental items ranging from knife-handles to chalices.[1]:73 The precise
quantities mined in any given year are unknown, but 18th-century leases
restricted output to 20 tons per annum. By 1892, the output is said to have
been limited to 3 tons per annum. Today, production is probably around
half a ton per annum,[1]:42 and the raw Blue John produced is kept within
Castleton where small articles, mainly jewellery, are worked and
sold.[1]:95 Elsewhere, similar blue and white-yellow banded fluorite
ornaments are now imported into the UK and other countries from China.[7]
A hand polished specimen (from Flickr
20
Literary References
The Terror of Blue John Gap is a short story by Sir Arthur Conan Doyle,
which appeared in The Strand Magazine of 1910 and describes the
experiences of a doctor who, while recuperating from tuberculosis on a
Derbyshire farm, investigates mysterious goings-on in a cavern mined for
Blue John.[8]
Alan Garner's 2003 novel Thursbitch features a cup made of Blue
John,[9] which becomes one of the links between its two narrative strands.
References
1.
^ :a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad Ford,
Trevor D. (2000). Derbyshire Blue John. Landmark
Publishing. ISBN 1-87377-519-9.
2.
^ George, Ken (2009). An Gerlyver Meur: CornishEnglish, English-Cornish Dictionary. Cornish Language
Board. ISBN 1902917847.
3.
^ Ford, Trevor D. (1994). "Blue John fluorspar". Geology
Today 10 (5): 186. doi:10.1111/j.1365-2451.1994.tb00422.x.
4.
^ :a b "History of the Blue John Cavern". Official site of
Blue John Cavern. Retrieved September 2010.
5.
^ The Crawford Cup, British Museum, retrieved 26
October 2012
6.
^ The Barber Cup, British Museum, retrieved 26 October
2012
7.
^ Graham Hill, John Holman (2000). Chemistry in
context. ISBN 0174482760.
8.
^ Conan Doyle, Arthur (1910). "The Terror of Blue John
Gap". The Strand Magazine 40 (236).
9.
^ Garner, Alan (2003). Thursbitch. The Harvill Press.
p. 22. ISBN 978-0099459361.
Much of the above from Wikipedia
21
POLISHING TIPS
Agates – Cerium Oxide on Canvas
Amazonite – Tin Oxide on Leather
Apatite – Line A on Leather
Amber – Tin Oxide on Leather
Aventurine – Tin Oxide on Leather
Azurite – Tin Oxide on Leather
Beryl – Cerium Oxide on Canvas
Bloodstone – Lin A on Canvas
Celestine – Tin Oxide on Leather
Chrysoberyl – Diamond Paste on Wood
Chrysocolla – Cerium Oxide on Leather
Coral – Tin Oxide on Leather
From the Summit Lapidary Club Inc. Ohio, USA via PGMC
These tips have not been tried by the editor so there is no guarantee that
they work.
Many lapidarists now heat nodule and thunder egg halves under a heat lamp
for a few minutes before polishing with tin oxide or cerium oxide on felt.
The polish comes up almost instantly. Alternatives include putting
specimens in a 200° F oven until they are warm to the touch or putting
specimens in hot water until they are warm. Dry off excess water before
polishing.
To spot cracks and vugs before sawing, first soak it in a tub of water for at
least an hour. Remove the rock and place it in a sunny spot. The surface will
dry quickly, but the fractures and vugs will not. Use a soft pencil to mark the
rock for guidance in sawing.
From Rockhound Gazette March 2012
22
•
Silver findings may be polished by filling a tumbler one-third full
of shredded newspaper. Place the findings in the barrel and tumble
for a few hours. Do not use any polishing compound and tumble
dry.
•
Turquoise: never use ammonia, soap or detergent on turquoise;
ammonia will turn the turquoise white. A drop of ammonia on a
scrap piece is a good test to see if it is genuine.
From Arrowhead News, Nov. 2008 via PGMS 1110
Stabilizing porous stones:
If you would like to try your luck at stabilizing porous stones such as
turquoise, so that it can be ground into shape and polished, then take a glass
jar with a lid, add half a litre of acetone, add the complete contents of both
the resin and the hardener tubes of epoxy glue. Mix well, add clean and dry
stones. Cover the jar and let it stand for at least 4 days. Remove the stones
and allow a week for them to dry completely. They should now be ready to
be worked with.
Come on you “Cabbers” give it a try and let us know if it worked. Keep
rocking, John Bruigom
Source: SA Lapidary Magazine, Nov. 2006 via Pretoria Rockhound Digest
The following were some of the tips noted during the February meeting of
the Beehive Rock & Gem Club:
• Diamond trim saws of 6 to 10 inches are most commonly used for making
cabs. Some types use water and have rust resistant blades while others use
oil (if water is used they must be drained each time used or they will rust
out quickly.
• Use a soft brick to “sharpen up” diamond blades. This cuts away some of
the metal to expose diamond edges.
• Diamond grinding and polishing equipment has distinct advantages to the
older and less expensive silicon carbide equipment (not as messy, quicker
results, not the wheel dressing needs, etc).
• Silicon carbide wheels need to be turned to spin out excess water at the
end of work so they don’t soften up or come apart. They need to be trued up
if wear is uneven across them.
• You don’t need to have a water hookup as you can use sponges to wick
the water to the wheel from the tray.
• Use the whole wheel (diamond grinder) by starting your rough grind on
the edge parts and finish more towards the middle to keep from catching an
edge.
23
Don’t “EVER “ - drain cuttings or water from your equipment
down the drain
(unless
you
want to buy a
new
sewer
system).
This
stuff sets up like
cement in your
pipes.
• Cat litter is a good to
absorb oil out of slabs
that have been cut with
an oil saw. Some dish
soap and water help
finish the cleaning.
• Agate is more forgiving
to work for cabs than
softer rocks & easier for beginners for that reason.
• Templates of different sizes and shapes help to “pre-form” type cabs for
which there are metal findings (settings) in silver, etc are readily available
so you don’t have to be a silversmith. Free form cabs usually
require special custom settings or wire wrapping.
• 3/16th is the most common thickness cut for cabs. For higher crowned
cabs or double sided cabs greater thickness are needed.
• Rocks that require great care grinding as dust can be harmful include:
Tiffany Stone, copper ores (Malachite, etc) and shells. More water and
masks help.
• Many types of things can be used for Dop Sticks including nails, flat end
bolts, etc, The use of double sided tape to attach the rock was of special
interest.
• Salvaging thin cuts and special types of fractured rock by gluing on
doublets with epoxy then finishing a cab was intriguing. Also by changing
the colour of the base under translucent or thin types of material can change
the appearance and colour of the cab.
• By using vinegar or another acid based product with the polish (tin oxide)
can quickly bring out a high glossy finish.
• A methodical approach is needed to work larger and flatter cabs as ―flat
spotsǁ become a nemesis to good work.
• Check cabs when they are dry rather than wet when moving through grit
sizes to see the scratches which need to be removed.
• One of the steps includes cutting a slight bevel in the underside of the cab
to prevent chipping at edge points.
•
Assembled by Rocky Ray of the Beehive Rock & Gem Club via Rockhound Gazette 04/12
24
Bubble Lace Agate
Illustrated is a pendant created by Georgie Sturmy recently. The spectacle
setting (i.e. viewable on both sides} in sterling silver contains a Mexican
Crazy Lace Agate.
This super rare type of lace agate is
rarely seen any more it is
sometimes called Noreiga lace
agate and is the most defined of its
type and highly prized by
collectors.
My Lexicon Records Noriega Lace Agate, near Benito
Juarez, Chihuahua, Mexico. Cross*
(1996.p.74) stated the name was
derived from Juan Noriega, one of
the pioneer miners in the original
lace agate claims in the Sierra
Lucia. It is a vein agate that has
formed in marine limestones of of
late Creaceous age.
* Cross, B.1996 The Agates of
Northern Mexico , Burgess
International Group, Inc. Burgess
Publishing,Edina, Minnesota
Georgie Sturmy & Colin Lansdell
25
In a recently purchased American book* I came across a reference to
Stockdale Beck agates. On e-mailing the author she was unable to give me
the location more accurately than “Cumbria” so I had to find it for myself.
The first thing I found was a synopsis by the Dept. of Earth Sciences, from
which the following extract is quoted:
‘Metamorphic effects on agate found near the Shap granite, Cumbria,
England: as demonstrated by petrography, X-ray diffraction and
spectroscopic methods
Agates from a 430 Ma host at Stockdale Beck, Cumbria, England have been
characterized. The crystallite size of the Stockdale Beck agates was found
to be ~60% greater than any other agates from five regions aged 400-1100
Ma. Raman spectroscopy identified moganite in all agates tested except
those from Stockdale Beck. Infrared spectroscopy showed that the silanol
content of the Stockdale Beck agates was near zero. The properties of
agates from Stockdale Beck and the 1.84-3.48 Ga metamorphosed hosts
found in Western Australia were similar but different from agates found in
other hosts aged 400-1100 Ma. Cathodoluminescence demonstrates further
differences between agates from hosts aged 13-1100 Ma and those from
Stockdale Beck and Western Australia. Agates from the latter areas have a
lower proportion of defects causing a red emission band (~660 nm) but an
increased proportion of defects causing blue (~470 nm) and orange (~640
nm) emission bands. Agates found in hosts aged 13-1100 Ma are also
differentiated from the Stockdale Beck and Western Australian agates in a
ternary plot of the relative intensities of violet to blue to orange emission
bands. Single scans producing this combination of colours are only found in
the Stockdale Beck and Western Australian agates. The properties shown
by the Stockdale Beck and Western Australian agates demonstrate that an
agate or chalcedony infill can be used to identify post-deposition
palaeoheating within a host rock.’
This synopsis was originally taken from: Mineralogical Magazine, August 2007,
Vol. 71(4), pp. 461–476 and is by Moxon, T. et al
* Brzys, Karen A., Agates Inside Out, 2010 Gitche Gumee Agate and
History Museum, Grand Marais, Michigan
Stockdale Beck is situated approximately 10 km north of Kendal at the
northern end of the Longsleddale valley at NY 49182 05469. I can supply
fuller directions on request.
I regret that copyright restrictions do not allow me to show an agate.
Colin Lansdell
26
ROMAN EMPIRE
Power & People
At the Norwich Castle
1 Feb – 27 April
Roman Empire Exhibition explores the story of one of the most powerful
empires the world has ever seen, and includes over 160 stunning pieces
from the British Museum. Norwich Castle is one of only six UK venues to
host this remarkable exhibition.
Highlights include sculpture from the villas of the Emperors Tiberius and
Hadrian, coins from the famous Hoxne treasure, beautiful jewellery and
near-perfectly preserved children’s clothing from Roman Egypt.
The exhibition explores the wealth, power and organisation of the Empire,
but also how the Romans viewed their provinces and other peoples.
Religious, military and personal objects give an insight into the lives of
people from northern Britain to Egypt and the Middle East.
Fascinating artefacts from the Castle’s own collections will also be on
show, including important religious objects, magnificent glass and pewter
vessels and wonderful Roman jewellery.
Remaining Tuesday lunchtime talks 12.30 – 1pm
4 March - Becoming Roman? The Empire
and East Anglia
18 March – The Roman Glass Industry-An
Innovator’s Paradise
1 April - Egypt under the Roman Empire
8 April
- Personal Adornment and Identity in Roman Norfolk
27
Mar 1-2
Mar 8-9
Rock Gem & Bead Fair
Oxford Colloquium
Mar 8-9
Mar 9
Rock & Gem Fair
Oxford Mineral &
Fossil Show
Rock Gem n Bead Fair
Rock Gem & Bead Fair
Rock Gem n Bead Fair
Rock n Gem Fair
Rock Gem & Bead Fair
Oxford Mineral &
Fossil Show
Rock n Gem Fair
Rock Gem n Bead Fair
Oxford Mineral &
Fossil Show
NAMHO Annual
Conference
Rock n Gem Fair
Rock n Gem Fair
Rock Gem & Bead Fair
Oxford Mineral &
Fossil Show
Rock Gem n Bead Fair
Rock Gem n Bead Fair
The Rock Exchange
Gem n Bead Fair
Rock n Gem Fair
Rock Gem n Bead Fair
Rock Gem n Bead Fair
Oxford Mineral &
Fossil Show
Mar 22-23
Apr 12-13
Apr 26-27
May 3-4
May 10-11
May 11
Jun 7-8
Jul 5-6
Jul 14
Jul 25-27
Aug 2-3
Aug 9-10
Aug 16-17
Sep 14
Sep 20-21
Oct 4--5
Oct 11-12
Oct 25-26
Nov 1-2
Nov 8-9
Nov 22-23
Nov 30
Cheltenham Pittville Pump Rooms
Visit www.ogg.uk.om
Mineral Symposium, Geofest 2014,
Lectures, Field Trips, etc.
Kempton Park Racecourse
Exeter Hall, Kidlington, N.Oxford
Brighton Racecourse
Newton Abbot Racecourse
Newark Showground
Bath & West Showground, Shepton Mallet
Newmarket Racecourse
Exeter Hall, Kidlington, N.Oxford
Kempton Park Racecourse
Newcastle Racecourse
Exeter Hall, Kidlington, N.Oxford
Bangor University, Gwynedd
Kempton Park Racecourse
Royal Welsh Showground, Builth Wells
Pavilions of Harrogate, Showground
Exeter Hall, Kidlington, N.Oxford
Newark Showground
York Racecourse
Lady Manners School, Bakewell`
Newton Abbot Racecourse
Kempton Park Racecourse
Pittville Pump Rooms, Cheltenham
Brighton Racecourse
Exeter Hall, Kidlington, N.Oxford
IT LOOKS AS THOUGH EARLY MARCH IS GOING TO BE A
BUSY TIME – PARTICULARLY IN OXFORD!
I have just found this in GeoSuffolk Times and didn’t have space for it
elsewhere. ‘Norfolk Museums and Archaeology Service’s Shine a Light
project will display the West Runton Steppe Mammoth at Gressenhall Farm
and Workhouse collections superstore from next summer [2014]; it may then
be viewed through tours, events and online.‘
28
NORFOLK MINERAL & LAPIDARY
SOCIETY
Founded 1973
Affiliated to G.A.
www.norfolkminandlapsoc.homestead.com/
Chairman: Christopher Marsh, 25 Carrel Road, Beacon Park, Gorleston,
NR31 7RF 01493 604778 c.marsh50@btinternet.com
Vice Chairman & Field Trip Co-ordinator: Richard Belson
01603 413003 dickbrid@btinternet.com
Secretary and Editor: Colin Lansdell
10 Lorraine Gardens, Norwich, NR3 4DH
01603 404833 clansdell@btinternet.com
Treasurer & Membership Secretary: Peter Smith,
15 Pitchford Road, Norwich, NR5 8LQ
01603 471536. treep2@ntlworld.com
Web Master:
Martin Stolworthy, 01603 872420 martin.stolworthy@btinternet.com
st
MEETINGS: 1 Tuesday of most months at the Catholic Church Hall,
Churchfield Green, Thorpe St Andrew, Norwich from 7.30pm.
Stone Chat is the quarterly publication of the society and
reproduction of articles is allowed (unless stated otherwise), provided
source and author are acknowledged. Opinions given in this
publication are those of the author and not necessarily those of the
Society. Information given by a writer is not always checked for
accuracy. Articles are accepted for publication on the understanding
that they do not infringe copyright laws (past or present) and that this
is the responsibility of the author.
30