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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 77 - Sunday 10/26/97
2. NEW: Cat's Eye Alexandrite
3. NEW: How Thick is a Cab?
4. RE: Clamping Rocks in a Saw Vise
5. RE: Vertical Lap Problems
6. FS: Fire agate


Subject: LapDigest News for Issue No. 77 - Sunday 10/26/97

There is a list of rockshops and mineral dealers in the US,
by states, at George Campbell's OsoSoft Mineral site:
<<>>. After
you access it, just follow the links. This list of shops
seems fairly complete, if one can judge from the list of NC
shops. If your favorite rockshop is missing, why not use the
link they provide and give them the info on the rockshop?
Let's make these lists as complete as possible and help
everybody out!

I contacted Reynolds Chemical, the people who make the
Reynolds polishing powders, and I hope to be able to bring
you some detailed tech info on these polishing powders soon.
If you remember, this was discussed briefly in Issue 57,
where Dick Friesen said: "If you want a real treat, polish a
piece of obsidian with cerium oxide, then polish again with
the Reynolds .2 micron powder. I usually have trouble finding
the surface with a ten power loop." Now that is AWESOME!!
These polishing powders come in 0.2, 0.35, 0.8, and 1.5
micron sizes, and are available in 4oz, 1lb, and 5lb packages
from Diamond Pacific.

Also, I contacted Lortone, and sent them the thread file on
"Leaking Lortone Lids", and asked them to comment on the
issues raised there, particularly on why pressures or vacuums
occur and how you can keep them from happening. Hopefully we
will get some authoritative info on tumbler behavior and on
better ways to operate them.

The very long thread, 'Polishing & Dyeing Geodes & Agates',
has been converted to two thread files:
(PolishingGeodesAgates.txt) and (ColoringGeodesAgates.txt),
and these two files are now in the Archives. You may get a
list of all information files by downloading
(ListOfInfoFiles.txt) from the Archives <in all cases,
without the parentheses, of course>.

Channel Work is a technique of mineral inlay, similar to
cloisonne in concept. Sterling silver strips are used to
construct a framework of cells, and this framework is
soldered onto a silver plate backing. Then different colored
rocks are cut to fit exactly into the cells, are glued in
place, and the whole is sanded and polished. I have asked
one of the best practitioners of this art to write up a
detailed "how-to" article, and he agreed. I look forward to
publishing it. If any of you have questions about channel
work, please send them in and we will publish all of the
questions along with his article.

Have a great week, and above all, have fun!


Subject: NEW: Cat's Eye Alexandrite

Hey Hale,
I am cutting a piece of cat's eye alexandrite. I remember
you had posted a question concerning length/width/height
ratios for cutting cabs. I had collected all the responses
you received, but lost the file when I re-formatted my hard
drive last weekend. Did you keep copies of the responses?
If so, please, please, please send me a copy! I want to get
this baby right! Also, I'd like to use the notes for The
Cape Fear club's November newsletter.

Bought the rough from Olympic Mountain Gems--$38. per carat
from 1-3 carats. This piece is 2.93 cts. I'm scared to
death of messing it up!! It's a beautiful seafoam green
with a pale wine-colored red, nearly transparent. Can't
tell yet how sharp the eye will be, but it's a very intense
white! I had ordered two pieces but sent a 2.68 ct piece
back. I felt that the yield would be poor due to the size &
shape of the crystal--slanted rectangle /=/ . With extreme
luck, I would have gotten a 5x3 oval out of it.

Hope you can help me out! If not, feel free to add this note
to the next Lap Digest!

Ed. Note: Unfortunately, Deb, I also lost that file in a
disk crash several months and a couple of computers ago. But
I would like to see it redone here. See below. hale)

Subject: NEW: How Thick is a Cab?

For most of the cabs I cut, and most of the bolas, I set my
saw to make slices about 3/16 to 1/4" wide - usually closer
to 1/4". This gives a smooth curvature on the usual size
cabs I make and seems 'right', but I had never seen this
discussed. Obviously, Deb (see above), cutting a cat's eye
will need a thicker cab than this. And moonstones also need
a thicker cab.

Does anyone have a good idea of the relative thicknesses
needed for different sizes and for different shapes of cabs,
and the different thicknesses needed by different sizes of
cabs of different materials?


Subject: RE: Clamping Rocks in a Saw Vise

I have a variety of odd shaped wedges that I use. Some of
them are hard wood, some are soft. I also use "plates" of
hard and soft wood to get a grip on the rocks. The most
important points are getting contact on at least three areas
of the rock and then clamping so tight that you cannot twist
them out of the vise.

Another trick is to mix either plaster of paris or mortar
cement into a milk container with your rocks (great for small
pieces). Place the rocks into the container so that each rock
is surrounded by the "mud" and let set up for a few days.
Then peal the container off and clamp into your vise and
start cutting. (By using a cementious material-NOT concrete,
the sand aggregate will also aid in sharping the saw at the
same time. If you break up small pieces of a grinding wheel,
you can cut lots of jade by doing this trick with no problem
of binding.
Another trick is to use a matching size of wood that has a
smooth face and match it with a smooth face of a cut rock.
Glue this with a water soluable glue and cut it until the
last cut, then soak it off in water to retrieve the last

Better yet, get some Aluminum angle and then dop a rock on
it! Heat the aluminum and rock with one of those disposable
propane torches. This works only with a cut rock (flat face).
This is a good solution and best for the time factor as you
don't have to wait for the glue or cement to cure before
cutting. Dop it as you would any stone-clean, free of oil,
etc. This is great for getting good material out of a heel.
Found this tip in a Rocks & Gems magazine. Or maybe Gems &
Minerals...I don't remember.
Ed. Note: Thinking about my problem of clamping optical
quartz for the sawing of cover slips for doublets, I noted
that the jaws are now lined with maple, which is very hard.
When the quartz is clamped up tight into the maple, it still
only makes point contacts. If I had a crushable wood on the
jaws, the quartz could crush into the wood fibers and the
contact then would be an area, giving much greater friction.
I went on Woodworkers newsgroup and asked about crushable
woods; the advice I got was to try poplar or basswood, which
I will do this week. They also suggested that I might use
rubber heels - or something similar - which is also worth a
try. Yes, I know I could glue it to a piece of wood, but
doing something new and different is more fun!! hale)

Subject: RE: Vertical Lap Problems

When I was poor, that is all I had; one disc, a tube of
Feathering adhesive (available at most automotive stores),
and a bowl filled with water that I would dip my fingers in
and splash onto the paper. When it would load up, I would
sponge it off or wipe it with a wet rag. I cut a lot of opal,
turquoise, variscite, malacite, lapis, and some agate and
host of other stuff. It worked fine for years until I could
finally afford good equipment. Wet/dry paper is cheap and a
pair of old scissors cuts circles just fine. Just try and get
the heavier kind of paper so that you are not always picking
small pieces of paper off of the neoprene disc-the feathering
glue works too good sometimes. Hold the cab up to your neck
as you are working, and that will tell you if you are getting
the stone too hot. Remember that most of the earlier people
didn't use water at all to cut stones, but sanded dry (wear a
disposable mask to keep the dust out of your lungs). Don't do
this with metals such as malachite which is copper carbonate!
You will get copper poisoning. I was sick for 2 or 3 days and
thought I was going to die burning up with a fever. For
azurite or malachite, use plenty of water to keep the dust at
a minimal, and wash your hands. If you smoke, you will have a
pleasant sweet taste in your mouth, and that is a great sign
that you've ingested much copper. A little copper will not
kill you, but a lot can make you wish you never saw that damn

By the way, the natives in Mexico who cut opal never used
water but cut everything dry. The secret for opal is to heat
or cool slowly. It can take both extremes, just not suddenly.

Brewster McShaad
non-commercial use authorized

Subject: FS Fire agate

Have 10 pounds of fire agate. No idea from where. Reasonable
material, no windows just rough. $175.00 for the lot, Plus

Thanks and best wishes

Gemstone Brokerage Associates Ltd. Telephone (518)438-5487
P.O. Box 8930 Albany, N.Y. 12208
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