LAPIDARY DIGEST
Administered by Hale Sweeny (hale2@mindspring.com)
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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 25 Monday 7/14/97
2. RE: Sugilite Rough
3. RE: Storing Opal
4. RE: Storing Opal
5. BIO: Bob Smith
6. BIO: John Dodds


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<MSG1>
1. LapDigest News for Issue No. 25 Monday 7/14/97

I have attempted to make the Archives more useful, and you will find two new
files there which may help. First is a file named Contents.txt, which
contains the tables of contents from every issue, issue by issue. Then,
these have been rearranged in a file named Index-24.txt to show the contents
of all issues through the 24th, thread by thread. There is a lot more work
to be done to organize the Index, but the dog work has been done.

One subscriber asked whether the Lapidary Journal really had changed over
the years, saying that he had been away from lapidary work for the last
decade or so. Yes, it really has changed, and it is now more into jewelry
and metal working and polymer clay beads and such. There are still some
lapidary articles in such areas as carving. But not many. I don't think
lapidary subjects are covered by any other magazine now, but if anyone knows
of a magazine where lapidary is covered, we all would like to know!

Another subscriber said that he treasured his collection of old Lapidary
Journals, as he could look up old articles. Well, Lapidary Journal published
an index to all articles from 1947 through 1991, and has a reprint service
which allows you to order reprints from the old issues. Descriptions of how
to do this are contained in the file: LJReprints.txt, which is in the
Archives.

Finally, Albert Zabinski wrote to say that he has listed data for over 900
clubs at his web site: <<http://bankswith.apollotrust.com/~zabinski/>>. The
listings are by State and City, with the club name, mailing address,meeting
times, and meeting location if all was available. If your club is not
listed, or if the data for your club has changed, please send the updated
information to him by e-mail to <<zabinski@bankswith.apollotrust.com >>. We
thank him for his work on this; it will be a valuable resource for all of us!
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<MSG2>
Date: Sun, 13 Jul 1997
From: R-Orion@postoffice.worldnet.att.net

Subject: RE: Sugilite Rough

In Issue 24, Carla said:
<<At a recent rock show I was looking at a piece of sugilite rough. It had
a shiny appearance and the seller said he had rubbed it with olive oil. >>

Since sugilite is blasted from a hard-rock environment, it's notorious for
small hidden hairline cracks. Since oil is frequently used to hide hairline
cracks (i.e., in rough and cut opals and emeralds, to name just a couple of
examples) I'd be very wary about buying oiled sugilite. But sugilite's
value can easily meet or exceed the $200 price quoted to you, especially if
it has cuttable quantities of Richterite, which I suspect is the name Carla
couldn't remember. Color is the main consideration in valuing sugilite and
many other stones. Fine, clean royal purples, magentas and red-violets
(without black veining) bring high prices, and the highest-priced pieces are
slightly translucent faceting grades.

The material was originally marketed as "Royal Azel" and "Royal Lavulite,
and in 1982 (according to the Lapidary Journal) facet-grade material was
being marketed in a range from $60 to $1,000 per carat. I have no idea of
current prices (except I bought a pound of nice smaller cab-grade stones a
year ago for $300) but suspect they are lower than in 1982 because
additional supplies of material have been found in South Africa and it's my
impression that this beautiful material has not found its special "niche"
with the broad jewelry-buying public (I may be wrong about that -- it may be
the scarcity of top-grade material that's the problem).

While I haven't personally cut Richterite (I can't lay my hands on the
information I've squirreled away on it), my recollection is it brings very
high prices. More info, anyone?

As for polishing sugilite, my best results have been with chrome oxide,
although I've achieved very acceptable polishes with diamond compounds too.
For those who want more info, there were a couple of interesting sugilite
articles in the November, 1982 L.J.(*)

Rick Martin
MARTIN DESIGNS
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(*)(Ed. Note. The two references to sugilite in the Lapidary Journal for
1982 are:

Any Way It's Royal - The Story of Sugilite 82:11:1316
Grape's the Color, Sugilite's the Stone 82:11:1334

See the file: LJReprints.txt in Archives on how to get reprints from the
Lapidary Journal) hale
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<MSG3>
Date: Mon, 14 Jul 1997
From: R-Orion@postoffice.worldnet.att.net

Subject: RE: Storing Opal

I've been cutting precious opal for nearly 40 years and have learned only
one thing for sure about it: there's always something new to learn. Ofhand
I can't think of any mineral (with the exception of garnet) that occurs in
so many different guises as opal. That's what keeps it interesting.

As for storing wet or dry, I agree with Bob Foster: dry. I sometimes keep
my rough wet in glass domes just to simplify selection of new stones to cut.
But all my cut stones are dry.

Yes, some dry opals crack and craze. But the bottom line is that they will
anyway, eventually. Some opals are born to craze. Since opal has been an
intense interest of mine over the years, I've studied everything I can find
about it. Experts simply don't agree on the causes of opal stability and
instability, but here's what I've come to think over the years based on
reading, conversations with experts and my own experience.

As Bob said, all opal contains varying amounts of water. Australian opal
expert Len Cram's research indicates that good quality, stable Aussie
material has about 6% water. Years ago when I was digging for opal at Keith
Hodson's Virgin Valley mine in Nevada, Keith told me a couple of stories
that make me believe opal instability is caused by mining it several hundred
thousand years too soon!

Most Virgin Valley opal simply contains too much water when mined. Hodson
told me he'd taken newly-mined opals from the waterlogged montmorillonite
clay inside his tunnel out into the sun and, holding them to his ear, could
actually hear the tinkling sound as the opal crazed. Presumably, the
cracking occurs from internal shock as water vacates from the main mass of
opal too quickly. On the other hand, he said opal missed in mining and found
several years later in the mine-dumps outside, tended to have a much higher
percentage of stability. This was presumably due to slower dehydration of
excess water, allowing internal "adjustment" to the water loss. His own
method of determining whether opal was stable, he told me, was to toss it up
onto the corrugated tin roof of his cabin and let it dry out under the hot
summer sun. Anything that wasn't cracked by the end of the summer would be
stable when cut, he said. I guess this is okay if you own an opal mine ;o).

I observed the same process in action when I bought a beautiful parcel of
Australian opal much too cheaply. It cut gorgeous bright red broadflash
stones in the 20 carat range. And every one of them crazed less than a year
after cutting. I put one of them into water and now, a lot of years later,
it's still crazing -- even in water. The moral: the opal-seller knew opal
from that particular mine was "cracky" and I was a victim. He went out of
business shortly afterward. While most Australian opal is stable, I've been
told that production from new mines is viewed with great caution until proven.

Over the years I've developed the habit of putting all the opals I cut aside
for at least 6 months before mounting or selling them. Most problems -- if
there are to be any -- show up in that amount of time. And with Australian
material, at least, I agree with Bob: it's not a big worry. I've had much
different experience with Mexican and Brazilian opal, however. I don't
trust Mexican opal at all. Brazilian opal is okay if it's alluvial
material, but stones I purchased from the old mine in Piaui State were
temperamental.

As for dopping opal, I've never had one crack -- not even Mexican opals!! --
when I use the following method. Buy or build a dopping heater that uses a
100-watt light bulb as the heat source. Raytech used to sell the type I
use, but something similar could easily be made from a tin can or??.
Meanwhile, in a small tin can heat a chunk of green dop wax slowly until in
liquefies (don't let it boil!!). Pour the melted wax into a bucket of cold
water from a height of 3-4 feet and recover the little blobby wax "tektites"
that result. After drying, store them and a tweezers near your dop
equipment. Meanwhile, prepare a bunch of dop sticks by dipping them into
molten wax and flattening the wax against a piece of cold metal. When
dopping, place a "blob" of dop wax on each opal as it heats. When it melts,
run a waxed dop stick through the flame of an alcohol lamp and quickly
"grab" an opal with it from the dop oven. I almost forgot: keep a container
of cool water nearby and dip your fingers in it, as needed, while you're
shaping the dop wax to the stone. I usually do 20 or 30 stones at a time
this way and it goes quickly.

This has run on much too long, so happy opal cutting!

Rick Martin
MARTIN DESIGNS
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<MSG4>
Date: Sun, 13 Jul 1997
From: stoneage@vermontel.com

Subject: RE: Storing Opal

I've found that most Aussie opal is pretty stable. I keep it in water
because it is just easier to see it when I'm looking for a particular kind
of stone, color and pattern. In response to one of the opal messages, I
think that in fact opal contains water in two separate ways. I believe
that one of those is part of the molecular structure. Some opals also are
porous and absorb water. These are the ones that become unstable but
mostly because they are porous. When the water from them evaporates, they
become milky. and then they can break due to changes in internal pressures
from variable internal water distribution.

I think that many mexican opal, though certainly not all, fall into this
category, as do Honduran, South American and North American, ie. Idaho. I
have cut pieces of Mexican Opal which months after their cutting, suddenly
cracked. I have not, but on a few occasions, had this problem with Aussie
opal.

As to carving Mexican opal. I'd want to let it dry out for quite a while
before I carved it to see how stable it was. And personally, I'd be
concerned about carving it because of the changing stresses. But, frankly
I'm no expert and most of this comes from personal observation. And too,
there is still much Mexican out there that is stable and beautiful.
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<MSG5>
Date: Sun, 13 Jul 1997
From: Vanir97@aol.com

Subject: BIO: Bob Smith


Greetings all, My name is Bob and I have been interested in lapidary for
many years but am still an amateur. I have two rock saws and several
tumblers and one polisher. At the present time I am cutting and polishing
petrified wood bookends for friends. I have tried cutting and polishing
amethyst with poor results.
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<MSG6>
Date: Sun, 13 Jul 1997
From: schist@ou.edu

Subject: BIO: John Dodds


My name is John Dodds, and I haven't been working with lapidary for many
years. I am very interested in the methods and tricks in this area, so I
look to this list to better inform me. I am 18, and have worked in a
granite\marble fabrication shop for over 4 years in between school. The
only tool I can call my own is a medium sized saw, which leaves me without
polishing capabilities. This is the area I am most interested in learning
of from those of you on this list.

I'm happy to have been told of this list, and I look forward to reading
your posts soon!

John Dodds
schist@ou.edu
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