Administered by Hale Sweeny (

This list digest contains the following message subjects:

1. LapDigest News - Issue No. 20 Tuesday, July 8, 1997
2. NEW: Cutting/Orienting Rainbow Obsidian
3. NEW: Change in Opals Colors over Time
4. NEW: Sawing with a Fence
5. NEW: Tumble Finishing Cabs with a Vibrasonic Vibratory Tumbler.
6. RE: Are There Hand Methods For Lapidary Work? (Hand lapping)
7. Re: Bulk Slabbing of Nodules
8. AD: Gemstone Brokerage Associates Ltd


Date: Mon, 7 Jul 1997 17:50:21 -0400

Subject: LapDigest News - Issue No. 20 Tuesday, July 8, 1997

Please remember -
If you have a LAPIDARY TIP, please send the tip(s) to me at the address below (not to the lapidary address), and I will start accumulating them for fillers. Make the subject: LAPIDARY TIP or just TIP and it will go into a folder directly, and I won't acknowledge unless I need more information for publication. Please mention the source if you got it from a bulletin or such!

Hale Sweeny
Administrator, Lapidary Digest Mail List
Durham, NC

Date: Mon, 7 Jul 1997
From: Geri Arms <>

Subject: NEW: Cutting/Orienting Rainbow Obsidian

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 instead of a a circular rainbow. It was explained to me once but I have forgotten the directions. Can anyone help with this?


Date: Sun, 6 Jul 1997

Subject: NEW: Change in Opals Colors over Time

Sometime ago, I bought some finished Australian opal pieces which had a brown colored area on them, but good fire. I brought them home, put them in
water for about 20 minutes, after which they were removed and let air dry
at room temperature. Then they were put into 'gem jars' with a glass top and cotton in the bottom. They have been in these now for about 5-6 months.

Recently I looked at them and found that the brown areas are almost gone
from some of them. And they also seem to have lost some fire!

I have heard some people say that opals have to be stored in water, others
say it is not necessary. SIGH!

My questions are these: Why did they lose the brown colors? What is the best way to store opal rough or finished opals? More importantly, how do you NOT store them?



Date: Mon, 07 Jul 1997

Subject: NEW: Sawing with a Fence

Some time ago Hale and I discussed a fence for a trim saw to give
slices of constant width for intarsia.

My question relates to the advisability of using a fence when slabbing
small agate nodules ( less than 2 inch on my 6 inch Rock Rascal) to
ensure a straight cut and constant thickness in the absence of a rock

I don't seem able to get constant thickness hand holding the stone and
have already dished one blade by allowing the stone to twist
inadvertently, I don't want to wreck another !

Andy Parker, Team Leader Information Systems, Furness College
Work :-
Home :-

(Ed.Note: Andy has built a 'rip' fence for his trim saw; I have not built one for mine, yet, but have all the materials. All our correspondence on the design of a fence will be posted sooner or later. Meanwhile, the question remains as to the best way to cut uniform slices from a 2" nodule; perhaps the question should be how do you hold the nodule to effect the uniform slicing?)

Date: Mon, 07 Jul 1997

Subject: NEW: Tumble Finishing Cabs with a Vibrasonic Vibratory Tumbler.

I have a Vibrasonic vibratory tumbler with a 4 lb. single hopper and an
adjustable switch. This tumbler was made by American Gem Supply, New
London, IA. I have 4 hoppers and use one for each stage of tumble finishing

After preshaping a blank, I start cutting the cabochons on a 80 grit Galaxy
wheel and then use a 220 galaxy wheel, continuing till I get a properly
shaped cab.

I put my cabochons in a hopper with 4 tablespoons of 320 Silicon Carbide
(SC) grit and vibrate for 100 hours. After careful washing, they are put
back and run another 100 hours in 4 tablespoons of 600 SC grit. Finally,
they are run for 150-170 hours in mixture of cerium and tin oxides - I use
this mixture over and over.

At the start of and between each stage, all cabochons are checked for
cracks and fissures. (Grit from one stage can hide in cracks, and if not
eliminated, can contaminate the next stage.) They are also cleaned really
well to eliminate contamination.

The filler used in all stages is odd (but mostly triangular) shaped pieces
of aluminum oxide, normally used to burnish metal fastener parts. They were
obtained years ago, used, from a metal fastener manufacturer. When I got
them, they had decreased too much in size to use for burnishing their metal
parts. They were about 1/8" thick and ½" to 5/8" in size.

I fill the hopper at each stage with no more than approximately 1/2 to 2/3
cabochons and add the ceramic shapes so that the hoppers are usually 2/3 to
3/4 full. You start by adjusting the amount of water added to the hopper;
adding a little water at a time. When you reach the proper amount, the
mixture will cover everything and not run off. Adjustment of amount of
water is a matter of trial and error. Finally, the hopper is covered with
plastic glad wrap with a rubber band on it to reduce drying..


Knobs Lapidary - Kentucky agate cabochons - designer cabochons in Kentucky
red and black agate - other types of materials from all over the world.

Date: Mon, 07 Jul 1997

Subject: RE: Are There Hand Methods For Lapidary Work? (Hand lapping)

I hand lap on plate glass using 80, 200, 400 and 600 grit ( but only until I finish building my lap !) It is slow going but does work eventually. I apply a thick slurry of water and grit to the glass with a small paint brush and lap in a figure of eight motion. A separate sheet for each grit is probably a good idea but I get by with a thorough cleaning.

The glass does abrade slowly - taking on a frosted appearance but lasts long enough.

I visited a lapidary club recently where all the flat lapping was done
on 2 foot diameter 2 inch thick glass lens blanks !

The main problems are arm ache and getting a ggod grip on the stone, I
often dop a short stick on the back to help with the latter.

Andy Parker, Team Leader Information Systems, Furness College
Work :-
Home :-

Date: Tue, 8 Jul 1997 07:50:52 -0400 (EDT)
Subject: Re: Bulk Slabbing of Nodules

In a message dated 97-07-06 12:11:33 EDT, you write:

Hi George:

Very comprehensive explanation of your proceedure, thank you very much. As
I've got a couple of blocks worth of test material to run, I'll give your
recipe a shot.

<< I use the acrylic latex "Acryl-60" (Thoro System Products) as an internal plasticizer which also enhances adhesion to the rock being slabbed>>

I'm assuming here that this additive will be found in the Paint section? One
of the other difficulties with the process I use, is the losing of the end
cuts, which more often than not are a little more than end cuts. The gist of
your formula leaves me with the impression that the nodules to be cut will
literally be "glued" into the matrix. Have you experienced a significant
loss of end cuts during the cutting process, or do you find that these hold
in place regardless of shape? Without exception, all of the Snake Skin
nodules that I cut are very much smooth and rounded detracting from any
adhesion properties that would normally exist in a surface that is uneven.

<<The mix should "slump" less than applesauce but soft enough to be
able to poke it down easily around the rock.>>

Opinion time. While building up the molds, what's the detraction from doing
a dry stack inside the mold to evaluate quantity of material to be stacked
and layout. Place the stones in the order to be fit inside mold. Mix brew,
pour in enough to fill mold about 1/4. Dip future slabs into remaining
solution to allow total coverage of material, then stack into mold as per
laid out in dry run. Stack till stone pokes out of goo, pour more, stack
more till container is full. This method would guarantee fewer air pockets,
allowing better adhesion between forthcoming matrix and rock. What drawbacks
do you see from this?

<<Pure Acryl-60 latex can be painted as a primer on the rock to
enhance adhesion.>>

Should this happen at such a stage that the latex painted on the stones tacks
up, or is a fresh coat, then directly into mixture acceptable?

<<A milk carton is easy but can leave excess mortar
around the rock, leading to needless "sludge" being cut into the oil.>>

Something else disliked about using the Plaster Patch, is it's inability to
hold it's own form. Sounds to me that this Portland method will keep it's
own shape with out any external assistance. This would allow the stripping
of the carton from the molded stones decreasing swarf that is introduced into
the cutting fluid. By the way, what type of cooling fluid do you use? I'm
currently running with Almag oil, which could be a thread all it's own.
The estimated costs for your method are acceptable. If it proves to provide
a higher return on the number of slabs that I can achieve, the returns will
overcome the increased investments.

Thank You George! This is exactly the reason this list exists. I only hope
that I will be able to help someone else as much as you've helped me!

Mark: Thank You as well for your thoughts of the gang saw. Unfortunately, I
can hardly afford to pay attention, therefore the thought of putting several
saw blades on one arbor makes my check book run yelping into Yvonne's purse.
I am willing, but the placement of the decimal point is heading in the wrong
direction. When I get serious about making Fischerstone beads, then it will
be taken into consideration. But that's another thread.

Thank You again Mark.

Oh Hale, Thanks to you as well! I was supposed to be working on my "other"
website this evening! {:-{

G'nite All!


(Ed. Note: Thoro Systems Products home page is found at : Product pages follow.)

Date: Mon, 07 Jul 1997
From: "cj" <>

Subject: AD: Gemstone Brokerage Associates Ltd

My name is Joseph J. Lanese better known as cj. I am the president of
Gemstone Brokerage Associates Ltd. I would like to take this opportunity
to introduce our firm. G.B.A. Ltd. as a supplier of Cabochon and Facet
rough as well as faceted colored stones. Our new Web site at is complete and up and running less a few
bugs to be ironed out.

G.B.A. Ltd.acts as a broker-sales representatives for a variety of
companies and individuals in overseas countries thus we are able to bring you quality rough at reasonable prices direct from the mines. To give an idea of the types of rough we carry, our present stock includes: Rhodochrosite, Chrysophrase, Shattuckite, Chrysocolla, Fire Agate and Malachite.

Please stop by and visit our site or email us to subscribe to our
e-mail list of cabbing and faceting rough and finished gemstones.

Thank You and best wishes


Gemstone Brockerage Associates Ltd. Telephone (518) 438-5487
P.O. Box 8930 Albany, New York 12208
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