Administered by Hale Sweeny (

This list digest contains the following message subjects:

1. LapDigest News for Issue No. 92 - 12/8/97
3. SPECIAL: Cutting a Protected Idaho Precious Opal


Subject: LapDigest News for Issue No. 92 - 12/8/97

This is the last part of the special issue in doublets and
triplets, and contains two how-to-do-it papers; the first is
by Rick Martin, and covers the whole topic. The second is by
Susan Thompson, and is partly directed to Idaho Opal. (For
the curious reader, I thought it would take three issues,
and said so in the Intro to Issue 91, but it now seems that
all will fit in two issues.)

Thanks to all who have contributed: Hans Durstling,
Goeff Haughton, Darlene Monroe,John Patrick,Michael Sielaff,
Rick Martin and Susan Thompson.

If you have queries on any of these articles, please send
them in.Also please send in queries so we can get the Digest
started up again.

Stay safe, and have fun!



- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
About the author: Hi, everyone! My name is Richard Martin and
I live in California, about an hour (on a good freeway day)
from downtown Los Angeles. I've been cutting stones,
specializing in precious opal, for almost 40 years now
(yipes!) and have recently taken up faceting and carving.
I've studied gemology with the GIA and have been involved
with gem sales, both loose and in jewelry, for many years.
While mainly a self-taught metalsmith, I've taken residence
courses in San Francisco with Alan Revere and have had
enormous amounts of help from many other talented and
generous people. My background is mainly as a writer --
newspapers, public relations and advertising in my native
Idaho, and in Utah and the San Francisco Bay Area -- but I've
always been involved in some aspect of the gem and jewelry
business. I am now pursuing it full-time under the name
MARTIN DESIGNS, creating limited-edition and one-of-a-kind
jewelry. You mat contact me at:

About the article: These are mainly my own methods and
suggestions, with input from several experts. Other cutters
may disagree or have better ideas. Everything put forth here
is based on personal experience. I use a Diamond Pacific
Genie, but the methods should be easily adaptable to nearly
any sort of lapidary equipment. If you are new to opal-
cutting, I would recommend you spend some time studying the
subject before spending much money on opal rough. Go to
shows, talk with experienced opal cutters and read as much as
possible on the subject. There are good books and videos
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

An opal doublet consists of two parts: a piece of precious
opal that is too thin to be cut as a solid (sometimes called
a "natural"), and a black backing material. The backing
accomplishes two basic things. It provides strength for the
thinner opal and intensifies the colors and brightness of
some opals. Sometimes opals that are thick enough to be cut
as naturals are backed solely to intensify the color. In my
experience this is especially true of Australian "jelly"
opals and some semi-crystal opals from Brazil and Australia.

An opal triplet is made of three pieces: a backing and a thin
slice of opal, as described above, and a final top layer of
transparent material such as crystalline quartz. Triplets
make it possible to enjoy the beauty of extra-thin opal that
would otherwise be wasted. I have seen various other
materials used for caps including glass, plastic, and clear
synthetic spinel. My personal recommendation would be to use
nothing softer than quartz. Bulk optical quartz is readily
available. Some firms used to offer a variety of pre-cut
quartz caps in rounds, ovals, rectangles, marquises, etc. but
I don't know of a supplier at present. Most calibrated caps
available on the market in recent years have been cast from
glass in Germany since the Australian triplet industry (the
consumer of most of these caps) now uses glass for both caps
and backing. One source for calibrated "crystal" caps (I
don't know whether rock or glass "crystal") is Alpha Supply,
Inc., address below.

BACKING MATERIAL: This is largely a matter of personal
preference. Black is the standard color for maximum color
contrast but I have seen red jasper and materials of other
colors used. At various times I have used black obsidian,
black jade, basanite and black opal potch. There are
probably other good choices; black onyx might work. Of the
four my personal preferences are basanite (perhaps out of
habit) and plain black opal potch. For better quality
doublets I would only consider using opal. Obsidian tends to
be too translucent to my eye, and black jade can be both
difficult to find and a bit tricky to polish, generating too
much heat for an epoxied joint, in my opinion, although some
opal experts like Paul Downing strongly recommend it.
Basanite is the name given to a fine-grained
microcrystalline basalt that is dense and takes a very nice
polish. I used to collect my own and a mail-order source is
listed below. (Basanite is also defined as a "velvety black
quartz used for testing the color of the streak of metals
<touchstone>, and as black jasper." But the name is also
applied to the black basalt as described).

WHAT KIND OF OPAL? Let's pause and think a moment. Each
person reading this may have a different image of opal in
mind right now. Some will see chunks with fire lines
running through them, others will see the ultra-thin slices
that come from the wire saws in Australian triplet factories.
Others will see something entirely different. You'll have to
adapt these instructions to whatever type you're cutting.
The kind I have in mind is mainly the white/gray or "light"
opals that come predominantly from Coober Pedy, Australia.
Some dealers sell "triplet opal." This rough is too thin to
cut naturals but often has extremely bright crystal opal fire
lines running straight through the rough, edge to edge. This
type of material makes superb triplets as does the opal from
Spencer, Idaho (See Note at end below), because the
multiple fire lines are flat, wide and transparent. They are
separated by bands of white opal potch. I've cut hundreds of
triplets from the Idaho opal deposit, and it's amazing how
beautiful even the thinnest fire lines can be. With the
Idaho material one can often select the final flash color for
the triplet by grinding through a green layer, for example,
to expose a single red one. The fire lines can be seen from
the edge of the piece. This type of work takes extremely
careful, precise grinding and lots of practice, but the
results can be astonishingly beautiful

TRIPLETS: The next step is to flatten the still-rough side
of the opal. If you're working with material like Idaho opal
that may still have usable fire lines, use a thin blade in a
trim saw to cut as closely to the selected fire line as
possible. This can be tricky at first. Don't try to cut
right next to the fire line; leave at least 1/8" of opal
between the saw cut and backing. One way of making the saw
cut parallel with the backing is to notch a trial cut at the
right depth, then continue making notches all around the
circumference of the stone until the cutting line is clearly
established. Otherwise, if the opal piece is thin, simply
grind it flat as above. This is where a bit of judgment is
needed: how much is enough? Again, if you leave milky potch
it will ruin the appearance of the finished stone. I grind
well into the fire line...cautiously.

To test the finished appearance, here's another little trick.
Dip a Q-tip into Opticon (DON'T USE HARDENER!!) and "paint"
the opal with it. Then select a polished cap (or polish one)
and set it on the opal. Opticon will more closely represent
the finished look of the triplet after epoxying than water.
A rule used by Bob and Susan Thompson to judge whether a high
or low-dome cap should be used is this: with the cap in
place, hold the start at eye level and look through the side
of the cap. If you don't see color from the opal throughout
the cap and only see clear cap material, it's probably best
to use a low dome. A high dome should show color from all
angles. You'll quickly discover that thick caps magnify the
fire pattern while thin ones look more natural. I personally
like the magnification effect on some broad flashfire opals
but think it makes small patterns like pinfire look
unnatural. You'll have to experiment until you find a
combination you like. After testing the appearance, you
may decide to do a bit more grinding. Clean off the Opticon
carefully with acetone before proceeding to further grinding,
but just wipe it off if you're ready to glue the cap on.

SEALING: In cutting Spencer opal, there are sometimes
fractures in the thin opal section that some cutters
recommend sealing at this point, so the Opticon serves two
purposes. First, clean the opal thoroughly with a brush and
detergent, then with acetone. Then apply a coat of Opticon
(WITH NO HARDENER) and heat to about 150 degrees in an oven or
under a lamp for about half an hour so the sealer can
penetrate the fractures. Allow the stone to cool, then wipe
off the stone with a lint-free cloth. Leave a film of the
Opticon on the opal when gluing; the hardener in the epoxy
will also harden the Opticon.

If pre-cut caps are not appropriate or available, optical
quartz slabbed to the correct thickness can be used instead.
The side to be glued to the opal should be flattened on a
coarse wheel but not polished. The quartz can be shaped and
polished after gluing (see the special dopping instructions

APPLYING CAPS: You'll need the same supplies and arrangement
used for gluing the opal to the backing, as well as a lead
pencil with a fresh rubber eraser. Have everything arranged
in advance so all is handy and within reach. Mix the epoxy
slowly on a small piece of aluminum foil with a toothpick.
Avoid mixing air into it. When it's ready, heat it under the
lamp a bit to liquefy the epoxy and help air bubbles move to
the top. If bubbles are apparent, let the warm epoxy sit for
a time to allow them to break. Bubbles are the bane of
triplet-making. Air trapped between the opal and cap ruins
the appearance of the finished piece by forming shiny circles
that reflect light. The only way to cure this problem if it
is observed after gluing is to grind the cap off and start

Ready? Apply a VERY thin layer of epoxy to both the cap
bottom and the opal, then carefully slide the cap onto the
opal. The epoxy must be thin enough so it won't build up
around the edge of the cap. Applying caps can be complicated
by epoxy sticking to the fingers, so be patient and carefully
clean your fingers before touching the cap again. It's
difficult to remove epoxy 330 smears from caps. (In the
section on dopping I mention that 5-minute epoxy can be
removed from a stone with a scalpel blade, and this is
generally true with the kind I use -- Tru-Bond -- especially
when it's fresh; but don't let it dry for a long period
before removing it. Epoxy 330 dries much harder than the
5-minute variety). The positioning process is made easier by
using the rubber pencil eraser to move the cap around until
it's in the right place. Then place the light bulb a few
inches from the triplet and re-heat the piece gently. When
the epoxy appears to be fairly liquid, hold the pencil eraser
against the cap and use firm straight downward pressure to
force all air from between the two surfaces (you can see the
bubbles under triplet caps easily with an Optivisor). Keep
up the pressure on the cap until no more bubbles can be seen.

It's important to use as little epoxy as possible because the
heat will result in more #&^%$!!! epoxy than you ever
imagined could issue from a joint that size, and it will
stick to everything in sight! That's why you want to have a
layer of aluminum foil under your piece. If the foil gets
glued to the triplet, it can be removed a lot easier than if
the piece is glued to a table, a workbench or an innocent
bystander. And if the surface (or workpiece) isn't very
flat, the heated epoxy will work as a very good lubricant and
the cap will tend to slide away from the position you want it
in. This is particularly true if you keep the heat on so I
prefer to check the positioning fairly often for the first
hour or two, then use the heat lamp to hasten drying when the
pieces are tack-bonded. Sometimes I clamp pieces together
with clothespins or other appropriate clamps..

DOPPING: You can dop doublets or triplets for final finishing
by coating the backing material with a small amount of stick
shellac dissolved in alcohol as facetors do, then heat the
wax on the dopstick in a flame. The wax should bond nicely to
the shellac without heating the stone, but don't overheat
when sanding and polishing!. Another trick I sometimes use is
5-minute epoxy. Rig a support (I use a dopping jig for
faceting but another method can easily be contrived) to hold
the dopstick about 1/16" from the back of the doublet. Put
a drop of epoxy on the stone and another on the dopstick,
then align them, letting epoxy fill the small gap. Let dry
at least 12 hours. The bond will hold firmly, and when you
want to remove the stone from the dop place the stick
horizontally in a vise and use a thin jewelers' saw blade to
cut through the epoxy between the stone and stick. The
remainder can be sanded off or removed with a scalpel.

The same method can be used for dopping to triplet caps to
finish cutting the bottoms (or for nearly any delicate stone
that's hard enough to allow the epoxy to be scraped off, or
that can survive a soak in acetone which will soften the
epoxy bond after 24 hours or so. DON'T IMMERSE DOUBLETS OR

There's one final operation. You need to bevel the backing
material 30 or 40 degrees so the stone has a totally finished
look from the top and sides. The cap edge should be the
widest part of the cabochon. The opal layer should also be
beveled slightly under the cap edge but you have to be
careful: if you cut it too far an unattractive transparent
area surrounds the opal when viewed from the top, ruining the
stone's appearance. Just "cut a little and look a lot," as
the famous lapidary saying goes. Some people polish the
bottoms of their triplets. I usually just grind the bottom
to the appropriate thickness (between 1/16" and 1/32") and
remove any ugly grinding marks with a 600 wheel.

There, you're done. If you've chosen your materials
carefully and have paid attention to details, you should now
have a beautiful jewelry stone that will give pleasure for
many years. And the knowledge that all that beauty would
have remained hidden forever without your hard work should
make your enjoyment even greater.


BASANITE: A supplier for basanite rough and slabs is Idaho
Opal Mines, Inc., P.O. Box 3848, San Clemente, CA 92674,
owned by Bob & Susan Thompson. When in Idaho their phone is
(208) 374-5360; in California, (714) 496-4589; FAX (714)
496-6589. A claim owner at the Spencer location, Mr.
Thompson told me recently that all the Idaho claims are
currently closed to fee-digging. Unless you were fortunate
enough to have visited the mines in years past or can trade
for Spencer rough, no more can be mined unless the policy
changes. Mr. Thompson and other dealers still offer opal
"starts": pre-ground and backed pieces ready for capping, and
Mr. Thompson has some pre-faced rough available for sale. To
view some top-notch examples of triplet-making, visit the
Thompsons' web site:<>

BLACK OPAL POTCH: A supplier of plain (non-precious) black
opal potch for doublet/triplet-backing and other material of
interest is Don Clark at The Gem Garden
( or e-mail at,
phone (916) 221-4686, FAX (916) 221-4740.
By mail: 1340 Churn Creek Rd. C-9, Redding, CA 96003.

HXTAL epoxy is available from Conservators Emporium, 100
Standing Rock Circle, Reno, NV, telephone 1-702-852-0404,
according to a personal communication from Thom Lane. He
gave the price as 60 grams for $40.00 and two pounds for
$265.Another source according to Lane is Talas, 568 Broadway,
New York, N.Y. 10012-3225, phone 1-212-219-0770.

"CRYSTAL" CAPS in a variety of calibrated round and oval
sizes are available from Alpha Supply, Inc., 1225 Hollis St.,
Box 2133, Bremerton, WA 98310; phone (360) 373-3302, toll
free order line (1-800) ALPHA 11, toll free FAX (1-800)

W.L. Maison Opals, Inc. of Salinas, CA, is listed in some
directories as a supplier of triplet caps. I called to find
out what these caps are made of, and report with sadness that
long-time opal dealer and friend Bill Maison passed away on
November 12. His daughter told me the opal business has been
suspended, perhaps permanently. Watch for further
announcements about the business in the lapidary magazines.

Subject: SPECIAL: Cutting a Protected Idaho Precious Opal

{This article was written by Susan Thompson, and was first
published in January 1996 and February 1996 issues of The
Opal Express, a publication of the American Opal Society. and
is reproduced with permission. It's title originally was:
OPAL, but was shortened here to fit the format.

Bob and Susan Thompson are owners of Idaho Opal Mines, Inc.
P.O. Box 3848, San Clemente, CA 92674-3848. Their phone is
(208)374-5360(Idaho) or (714) 496-4589 (California). They sell
basanite rough and slabs and some opal rough. Their website
is at <>}
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

A triplet or "protected" opal is like a sandwich with the
usual thin layer of baloney. The delicate fireband is
sandwiched between a layer of black basalt and clear optical
quartz. Black is the best backing material to bring out the
strongest and most vivid color, although other colors may be
used. The following steps are recommended as a guide to
cutting triplets from Spencer, Idaho Opal. Your own
experience may invite other techniques, but the steps listed
below have been tried and proven.


Study and orient the raw material carefully, then gently trim
the excess rhyolitic matrix from the opal nodule (use a small
hammer and pointed chisel if necessary to facilitate sawing).


The fire in the opal lies in bands or layers between white
opal. Some nodules may have more than one band of fire so you
must decide how you can get the most out of the piece you are
working. If the bands are too close together to split with a
fine saw blade, you will have to choose the brightest and
most promising one. After you decide which band to work, saw
parallel to the band. It is difficult at first to saw exactly
parallel to the band so do not try to saw right next to it.
After the first cut is made continue to cut about
one-sixteenth of an inch deep until you are all the way
around the rock, then continue deepening and turning until
you are all the way through. Leave approximately one-eighth
of an inch of white opal between where you saw and the layer
of fire.


With a 100 grit silicon carbide or diamond wheel for
roughing, then 220 grit for finish, begin grinding away the
excess material from the fire band. Grind down until the fire
begins to show. Make sure plenty of water is used during the
process to keep the opal cool. Opal is very sensitive to heat
and can fracture easily. Be careful not to gouge the fire
band on the edge of the grinding wheel as you start the
finishing process.


Now you are ready to lap off the remaining white potch
covering the fire band; use a flat diamond lapping disc or
the side of the silicon carbide wheel until the fire band
shows its colors. Then, lap well into the fire band, usually
about one-third of its thickness. This will make sure there
is not any potch remaining on the fire band, which would
result in poor quality grey stones when it is bonded to the
black backing. To lap the fire band, use the side of a 220
grit silicon carbide stone or a 300 to 400 grit diamond disc
to make a flat surface ready for sealing.


Wash the fire band thoroughly using a soft toothbrush, water
and detergent. Dry the opal, then clean it with alcohol or
acetone to remove any oiliness. Next apply a coat of fracture
sealer to the opal and set it under a heat lamp, or in an
oven at 150 degrees, for 20-30 minutes. Allow the stone to
cool and wipe off the fracture sealer with a clean rag or
paper towel. Do not clean the fracture sealer off with
acetone or alcohol. Now you are ready to glue the backing
onto the opal.


Clean the basalt backing with alcohol or acetone since it was
cut with oil. Then, mix epoxy 330 and coat the opal. Place
the opal on the backing and press down firmly to make sure no
air bubbles are trapped between the opal and the backing.
Black paint powder or other colors may be added to the epoxy
for a more uniform black or different colored backing. If you
mix the epoxy too fast, air bubbles will develop---if they
do, let it set a few minutes to clear up the bubbles.


After the epoxy has dried, saw parallel to the backing
material, allowing approximately one-sixteenth of an inch
between the backing and the saw cut. It may be necessary to
split a fireband or cut between two fire bands, so examine
the stone carefully before you make the cut.


Grind and lap the opal and basalt start until you are once
again well into the fire band. You should try to capture the
center one-third of the fire band. Finish lapping with a 600
grit lap or 600 grit hand sandpaper. Be sure all scratches
are removed and the best color is obtained. This is the
exciting critical stage of lapping, usually the fire band
will be ground down so it is paper thin to obtain the most
brilliant color.


Again, with a soft toothbrush, detergent and water, scrub the
opal surface to remove any residue from the surface or in the
fractures. Dry the start in an oven or under a heat lamp at
less than 200 degrees. Then, clean it with alcohol or acetone
and dry it again which prepares it for sealing.


If the fire band has cracks in it, white powder grindings will
embed into them which must be cleaned out using the above
cleaning process. Then, while the start is still warming from
the oven or heat lamp, apply a layer of OPTICON CRACK SEALER
without hardener and let it cool. If cracks still remain,
heat and allow to cool a second time. Old cracks will not


Wipe off the fracture sealer. Using pre-polished optical
quartz caps or natural quartz slabs, select them for the best
size, place them on the opal fire band to obtain the best
color, pattern and size. Make sure the caps are clean and do
not touch (with your fingers) the surfaces that will be
bonded together. Using 330 epoxy, coat the fire band and put
the quartz caps in place, they can touch each other. Apply
enough pressure for all air bubbles to disappear and let the
epoxy dry. Air bubbles will look like a silver spot under the
cab. Watch to make sure the caps do not slip to one side
while the epoxy is still wet. This is especially true when
heat is used to accelerate the bonding action.


Now you are ready to finish your precious gems. Using a small
trim saw, score the back of the basalt on line between the
quartz caps, then break the basalt and separate your gems.
This separating method allows caps to touch each other and
not get nicked by the saw. Trim off all excess basalt
possible with the saw, dop the stone on the cap if necessary.
If you are using dop wax, make sure the edge of the cap is
visible all the way around the stone. Some people also dop
their stones with epoxy. Then, holding the stone edge ways at
a 30-40 degree angle to the grinding wheel, proceed to rotate
and grind the basalt backing to a uniform oval. Grind up to
the base of the quartz cap without touching it. Scrape off
any excess epoxy from the quartz cap and around its edge with
a knife which will not scratch it. Polish the caps as needed.
With a little practice you will be able to trim just under
the edge of the cap without touching it. This eliminates
having to polish the cap. The backing should also be ground
down to about one-thirtysecond of an inch thick. You now have
a beautiful triplet or protected precious opal ready to be
put into a beautiful jewelry setting.


If you are not using the pre-cut caps, glue the slab of
quartz on the start, mark out the size of stone you wish to
make, and cab it just as you would a piece of agate or other


If the steps above are followed, you can make triplets from
Idaho Opal that are flawless and beautiful. One error or
omission will result in a poor quality stone.


Many people ask which is better to use---a high or low dome
cap. Use whichever type does the most justice to the stone. A
simple rule to follow is this:

Try placing both kinds of caps on the start with water on it
before you apply the fracture sealer. This will give you an
idea of what the finished stone will look like. Hold the
start at eye level and look through the side of the cap. If
all you see on the high dome is clear quartz, then it is
probably best to use a low dome. A high dome should pull the
color into the top of the cap so the color is visible from
all angles.

The backing material does not have to be black. A red
material such as ruby jasper is very effective with some
types of fire. Plain white opal can also be used to give the
triplet a natural opal look, but also the protection of a
triplet. Quartz on both sides is very desirable for pendant
mountings that may turn over when worn.

Always remember, one of the biggest enemies of a triplet is
oil. Be sure to thoroughly clean each piece that may have
come in contact with any oil. Do not forget that there is oil
in your skin. Any pieces you touch should also be cleaned.

Always grind your opal carefully, and constantly watch to see
that you are parallel to the fire band. Remember...
Haste Makes Waste!

non-commercial republish permission granted
To subscribe to the Lapidary Digest, send a message to, with the word SUBSCRIBE DIGEST as
the subject of the message. Other commands you may use are:
UNSUBSCRIBE DIGEST to quit, HELP to receive a page of help
instructions on the use of the list, and DIR to receive a
list of names of all files in the Archives.

The command <GET filename> may be used on the subject line
(without brackets, of course) to obtain a copy of the file
named "filename". Type filename exactly as it appears in the
directory, including the extension txt. Do not cut-and-paste
filenames into the subject line.

Each author is requested to write the words
"non-commercial republish permission granted" at the end of
every item submitted. This gives permission for others to use
your item for non-commercial purposes. Please use those four
words at the end of each item you submit.