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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 27
2. NEW: Vibrating Lap Grit
3. RE: Vibrating Lap Grit
4. RE: Orienting Rainbow Obsidian
5. RE: Polishing Corundum
6. Re: Polishing Corundum (Star Saphire)
7. BIO: Lewis Elrod

Subject: LapDigest News for Issue No. 27

Among our members, we now have 3 members from Australia, 2 each from Denmark and the U.K., 1 each from Portugal, Sweden, Taiwan and New Zealand. Five members have the extension 'ca', but there may be many more members from Canada, as the .com designation is also used by some Canadians. Fifteen of us are associated with colleges or universities, having the '.edu' designation. In total, there are over 230 total subscriptions.

But the quality of a mail list is not to be judged by the size of the enrollment but rather by the service provided. If any of you have suggestions for improving the mail list, please send them to me at

I am happy to see that we have replies to two of the three recycled queries quoted in Issue 26. Now if only someone knew about treating tiger-eye, we would have a grand slam to our three recycled queries!

Date: Tue, 15 Jul 1997

Subject: NEW: Vibrating Lap Grit

Does anyone have a secret for making the slurry thicker for a vibratory lap? My 80 grit and 220 grit stay fine in the pan. The 400 and 600 grit are both light and want to vibrate out of the pan. Any ideas?

Mark Case (
Randleman, NC
Date: Wed, 16 Jul 1997

Subject: RE: Vibrating Lap Grit


Don't laugh, please! But I think some plain Metamucil, without flavoring,
would make an excellent start on a slurry which might just keep the smaller
grits in place. Metamucil contains ground up psillium seed, which is a soluble fiber. Dissolved in water, it forms a musus-type thick liquid. I tried it out in a tumbler as a way to get to a good slurry faster, and it seemed to work OK. I would not get a flavored one, as the coloring MIGHT stain the rocks - I don't know. Naturally, Wal-Mart has the cheapest version I have found. I mixed a glass of water (8 oz.) with 4-5 tsp. Metamucil, and got a rather thick liquid material, and used this as the starting liquid in the tumbler.

Other suggestions would be to put water and toilet paper, clean newsprint
(no ink) or even Kraft paper in a blender and blend to smooth; I have also
used this as an additive to aid making slurry in a tumbler. (Please no comments about where my mind is tonight!)

Hope these help.

hale <>

Date: Tue, 15 Jul 1997

Subject: RE: Orienting Rainbow Obsidian

Geri Arms ( wrote:
<<I have a large chunk of Rainbow Obsidian rough. I have been told that
there is a special technique to cutting Rainbow Obsidian to produce a heat
rainbow design instead of a circular rainbow. It was explained to me
once but I have forgotten the directions. Can anyone help with this.>>

The "Rainbow" comes from the obsidian being "layered", don't know how
the "layering" occurs. Each layer reflects light differently and gives
a single color per layer. (Maybe someone can give a more correct
definition of the physics of the process). The result is that to cut
for a rainbow you cut at an angle through the layers. The most common
angle suggested is 15 degrees but my experience is this is just a starting
point. Different pieces of obsidian will have different thicknesses of
layers and the angle of the cut can be adjusted to give better results.

Cutting parallel to the layers will give a Bullseye result which can be
attractive if the layers are thin. The "circular rainbow" comes from
the dome of the cab when the rough is cut at an angle. I have not
heard of the term "heat rainbow" but my GUESS is that it is caused
by a wave in the rainbow pattern. The layers are not always straight
and cutting through the layers in such a way as to intersect several
"rising and falling" layers may produce such an effect.

FYI: I have had better luck identifying the layering in the rough.
If the obsidian has been blocked on a slab saw I have a much harder
time orienting it.

Dick Friesen (
(Ed. Note: Having cabbed but never slabbed rainbow obsidian, I was intrigued by Dick's description. I researched the books at hand, and found the following in Sinkankas' 'Gemstone and Mineral Data Book' p337. Under the listing of minerals with special optical effects (included even tho obsidiam is not a mineral), we find: Aventurescence due to minute striplike inclusions or partings; sometimes coarse and spangly (Mexican); at other times extremely fine and then resembling the sheeny appearance of laboradorite (Oregon, California) and with somewhat similar colors. -hale)

Date: Tue, 15 Jul 1997

Subject: RE: Polishing Corundum

<<I have just cut my first Corundum (Star Sapphire and Star Rudy) cabochons... The problem is I'm not happy with the final polish. This is the hardest material I have cut to date. Is there a secret to obtain a high polish? The stages used were: 220, 280, 600, 1200, 8000, 14000 & 50000 grit (all diamond). Under water the stones look great. -- >>

Since most people don't wear -- or admire -- jewelry underwater, perhaps it
would be better to get a polish that looks good in daylight! ;o)

You don't mention something important: what kind of wheels/laps are you
using? I cut cabs on a Diamond Pacific Genie, and have found that my
technique with those particular wheels doesn't produce a high luster on
corundum (maybe someone knows a better way, and if so I'm eager to learn).

Until then, I'll continue to use either star cups or phenolic star laps.
I've found you need a very hard surface for the final polish on corundum
cabs. Once the cab is preformed and fine-ground, flats can be taken out
while it's still dopped by cupping a small sheet of silicon carbide cloth of
the appropriate mesh (around 220 or 325, as I recall) in the palm of your
hand and hand-sanding the cab until the desired final curve is established.
I know, it sounds tedious, but it's far faster than one might think and
saves a lot of time at the wheels.

Star cups use interchangeable copper inserts that can be charged with
various diamond meshes. They're available from many suppliers, and I happen
to be looking at the Alpha Supply catalog as I write. The phenolic starlaps
operate on the same principle but feature grooves that can be charged with
diamond (be sure to charge with fine grits in the center to coarser ones in
outer grooves to prevent contamination from centrifugal force).

After that it should be a simple matter of finding a combination of diamond
grits that delivers the desired polish. I think you're going through too
many stages. I quote from "How to Use Diamond Abrasives to Cut Gemstones"
by EMAC Books (still in print, available from Alpha):

"One recommended sequence for sapphire, ruby and garnet is to grind first on
180 grit and fine grind on 1,200 (both smooth surface metal bond, not
interrupted surface). For the smoothing and polishing with the grooved
phenolic laps, at least two diamond grits are required -- 1,200 and 8,000.
However, some craftsmen feel you will get a better polish if you use 600,
1,200, 3,000 and 8,000, and still better if you finish with 14,000."

Hope this helps.

Rick Martin

Date: Wed, 16 Jul 1997

Subject: Re: Polishing Corundum (Star Saphire)

If you are not getting a high polish you may want to check the following:
..Did you clean with soap and water between polishes? The diamond polishes
in paste form are not always easy to remove. Not cleaning will bring some of the coarser grits to the finer step.
..Make sure you spend enough time on each step. Saphire is hard material and takes a little more time and pressure.
..Make sure you watch the temp of the stone, I have seen them fly off the dop when overheated. Polishing more than one stone helps as you can rotate and let a stone cool while working on another.
I used to use a product called Linde A. It was a saphire polishing
powder in a slurry solution. It worked very well on leather for a final
polish. Someone else may recommend a different product if this is no
longer available.

Steve Ramsdell

Date: Tue, 15 Jul 1997
From: <>

Subject: BIO: : Lewis Elrod

I started as a "rockhound" when I picked up rocks that appealed to me. Still have some of those over fifty years later.

In college a crafts course was offered and I did some cabs and some silver work and was much intrigued by it all. Later came work, marriage and a child and not much time for hobbies, as many of us have learned. My wife began to want her ears pierced so my mother called a doctor and sent him a check to pay for the piercing. I purchased several pair of earrings for her and was not happy with the quality. I thought "I can do better than that" and began to make jewelry for her. Others seemed to like what I made and soon I had a small business going.

I got out of this when I discovered minerals began a collection. Now I am
back in the jewelry business on a part time basis and will soon have the
"Silver Fox Gallery" open for business on a part time, appointment only,
basis at Murfreesboro. I will specialize in jewelry, supplies for
rockhounds and in items made of Tennessee rock (petrified wood, coral,
agate, onyx, quartz geodes, onyx, etc.) This will be a good way to keep
busy after I retire from service with the State of Tennessee in a little over
a year.

Nineteen years ago I organized a meeting of a group of rockhounds. That group is now the Middle Tennessee Gem & Mineral Society, Inc. A wonderful group of people. Over 150 members, now planning our 17th annual gem show, give five scholarships per year, have supported the William Holland Foundation, and many other projects. I am really proud of them.

After the group was going I have served on the board of the Southeast
Federation of Mineralogical Societies two different times as Tennessee
Director. I now serve as the First Vice President of the American
Federation of Mineralogical Societies and am looking forward to the future as an officer with this group.

Any of you who have ideas to improve the hobby, to better serve the people who are so interested in this world of ours and/or who will be willing to help further our interests should feel free to contact me. The 1999 AFMS show and convention will be held in Nashville, TN inconjunction with the
SFMS convention in July of 1999. I am most interested in ideas you may
have for special features, speakers, exhibits, etc. I would like to have
the greatest spread of exhibits ever made East of the Mississipi if
possible. The talent is out there, just come on out and let your talents
and accomplishments be seen.
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