Administered by Hale Sweeny (

This list digest contains the following message subjects:

1. LapDigest #18 News (SUNDAY, JULY 6, 1997)
2. New: Arizona swap
3. Re: Bulk Slabbing of Nodules
4. RE: Bulk Slabbing of Nodules
5. Re: Treating Opal
6. Re: Treating Opal
7. Re: Treating Opal
8. Re: Treating Opal
9. Re: treating opal
10. RE: Are there hand methods for lapidary work?
11. RE: Are there hand methods for lapidary work?
12. RE: Are there hand methods for lapidary work?
13. RE: Are there hand methods for lapidary work?

Date: Thu, 3 Jul 1997 15:18:07 -0400

Subject: LapDigest #18 News (SUNDAY, JULY 6, 1997)

Hope all of you had a happy and safe Fourth of July holiday!

In this issue are two threads I find exciting. The first is bulk slabbing of nodules which Vince started in the last issue. This is but one aspect of the problem finding special ways to hold rocks of different shapes/sizes for sawing. I hope to see more on this thread and more on this topic.

The other thread of interest is hand methods in lapidary. These include, below: cabbing, lapping, drilling, knapping and carving! Amazing!

Hale Sweeny
Administrator, Lapidary Digest Mail List
Durham, NC

Date: Thu, 03 Jul 1997 17:56:22 -0400
Subject: New: Arizona swap

Is there anyone on the list in Arizona (preferably Tucson to avoid
postage) interested in slabbing a couple of fist sized pieces of
Bolivian sodalite (and polishing one side of one) for me, in exchange
for half?

Thanks, Dick

(Ed: Acceptances and subsequent correspondence about this offer should be done directly to Dick at and not through the Digest)

Date: Thu, 03 Jul 1997 21:26:38 -0400

Subject: Re: Bulk Slabbing of Nodules

As a saw matrix, I have found Portland more satisfactory than Plaster of
Paris because PoP must lose water in order to gain compressive strength
while Portland USES water to cure. I like Type III (High Early) Portland
because it can be locked in the saw within 36 hours after casting. It is far
stronger at 36 hours than PoP at 2 weeks (full dry). Since you can't use
aggregate (sand) in the Portland, I use the acrylic latex "Acryl-60" (Thoro
System Products) as an internal plasticizer which also enhances adhesion to
the rock being slabbed. Mix 1 part Acryl-60 with 3 parts water as the
liquid portion and figure 3-1/8 fl oz liquid per 8 fl oz "cup" of dry
Portland. For mixing, measure the rock volume by water displacement and
subtract from the molded volume (takes 2 inches head space to fit our saw to
cut 100% of the rock). Vol yield is (appx) 11.3 per "cup" dry
Portland. The mix should "slump" less than applesauce but soft enough to be
able to poke it down easily around the rock. Be sure to record the vertical
height of the rock to mark on the finished block to aid in setting the saw.

The molds are made from 1/8 inch plexiglas- One plate is permanently bonded
upright (exactly) to a base plate. A variable rectangular "case" is then
made from three more upright plates at mutual right angles. These are offset
laterally (to fit the dimension of the rock at hand) and a hobby hotmelt
gun seams the plates to each other and to the base plate, forming a leak
proof joint. The rock should be oriented with the saw kerf in mind. The
rock, if small, may have to be anchored to the base plate with a bit of clay
or dbl sided carpet tape to keep it's position when the portland mix is
loaded. Be sure to "poke" the mortar around the rock, filling clear to the
corners. Pure Acryl-60 latex can be painted as a primer on the rock to
enhance adhesion. If multiple rocks are embedded, it is better to "stack"
with a tad of plumbers epoxy holding apart in a vertical position, rather
than side by side because the blade often wants to "jiggle" when going from
one rock to another leaving an edge saw mark. I have mini-mold sets to
handle special small (down to 3/4" diam.) stones for stable use on a fine
cutting saw (manual feed).

The assembly can be peeled apart after about 18 hrs. The hotmelt glue will float free of the plexiglas if placed in a dishpan of moderately warm water. I recast and reuse the hotmelt just because it takes several sticks per
assembly. The plexiglas pieces will last forever and are totally adjustable
for face rectangle. A milk carton is easy but can leave excess mortar
around the rock, leading to needless "sludge" being cut into the oil.

Regular Portland works ok, too... but let it cure for at least 3 days.
White Portland is smoother and about as fast as High Early but twice the
cost. Regular Portland is half the cost of High Early, about $3.00 per bag
(trivial $ per rock). Acryl-60 is about $10 per quart but cheaper by the

* George Butts, KC8T
* Laurie Butts, N8CKI

Date: Thu, 03 Jul 1997 17:35:25 -0400

Subject: RE: Bulk Slabbing of Nodules

In Issue #16, Vince King wrote:

<<One of the duties performed in the production of Fischerstone involves
taking nodules of Snake Skin Agate, from the size of your first down to
golf ball size, and slabbing them. Current process includes blocking this
material in 1/2 gallon milk cartons with plaster patch as the bonding
medium. ... (snip) ...I am interested in reevaluating my S.O.P.,
incorporating as much knowledge as you are willing to impart.>>

If it was me, I might consider a gang saw. If you are doing that much
slabbing and everything is blocked, you can do 4-5 slabs in one pass. And
from the size of your workpieces, you would need a 6" & 10". This would not
run into that much money. I would say 3-4 manufactures in Idar-Oberstein, Germany would have them on the shelf stock. You can even find equipment there to cube it. All kinds of state of the art equipment. I also would use sintered blades, if you are not already. Larger initial capitol outlay but Lower cost in the long run. You have Edus, Winter & Lux as the three main manufacturers there. But you will find even the hardware stores there carry automatic cutting machinery, cobbing hammers, diamond blades,...the works. The whole town is a lapidary city. If you go in September for the annual show, all the equipment will be on display.

Mark Liccini
Gemstone Rough Dealers since 1970 U.S.MAIL
E-Mail: 107 C.Columbus Dr.#1A Jersey City,N.J.07302
Voice Mail/Fax: 201-333-6332

Date: Thu, 03 Jul 1997 17:45:45 -0400

Subject: Re: Treating Opal

In Issue #17, Ron Lupo wrote:

<<Hello all, Since this treatment with acid is only leaving a black carbon
residue, is this a permanent treatment or will it eventually wear off?>>

It is very stable, but sometimes only 1-2mm under the surface. If you recut the stone, you can go through it. I guess this would classify as a diffusion treatment.

Mark Liccini
Gemstone Rough Dealers since 1970 U.S.MAIL
E-Mail: 107 C.Columbus Dr.#1A Jersey City,N.J.07302
Voice Mail/Fax: 201-333-6332

Date: Fri, 04 Jul 1997 12:52:22 -0700

Subject: Re: Treating Opal

(Same query as above)


Since the treatment is a fair surface penetration I would consider the
treatment to be permanent. Granted severe surface abrasion would most
likely affect the appearance of the treatment but then again surface
abrasion would affect the appearance of any cabochon as well.
best wishes

GBA Ltd.


Date: Sat, 5 Jul 1997 11:44:24 +0000

Subject: Re: Treating Opal

(Same query as above)

Hello all

Permanent treatment - the black is in the interstices of the stone.

Mel Albright
Hug or call a loved one today!

Date: Sat, 5 Jul 1997 13:42:06 -0700

Subject: Re: Treating Opal

(Ed: Gary started this thread by asking how to treat Louisiana opal he had bought at a show.)

I was advised off-list to read "All About Andamooka Opals" before attempting the "burnt sugar" treatment on Louisiana Opal which shares similar visual
characteristics with Andamooka Opal. I called the author to order the book
and he said that Louisiana Opal will not respond properly to the treatment.
He has tried it himself. ( I also determined there's a good chance that
he's the dealer I purchased the material from originally.) He advised that I
cut, polish and dry the cab, and not stabilize it. Drying, he said, will
promote maximum color.

Gary Ogg
Columbia, SC

Date: Thu, 03 Jul 1997 17:44:18 -0400
Subject: Re: treating opal

Is there really opal found naturally in Louisiana? I have heard that
only Tegucigalpa has more Hondurans than New Orleans- Gary's material
sounds a lot like Honduran Galguiere before they "burn" it. If so,
opticon works, but doesn't penetrate very deeply (not having any vacuum
equipment, I used to retreat after each grind). Eventually you learn to
recognize some little spots will remain porous even with opticon- these
can be treated with super glue!

Regards, Dick

Date: Thu, 3 Jul 1997 15:35:15 -0400 (EDT)

Subject: RE: Are there hand methods for lapidary work?

(In Issue 17, it was suggested that a hand cabber fit the question)
I've never heard of a Lortone hand-cabber. How do they work, and where would one buy a Lortone hand cabber??

Sundries for soapers gift baskets , BOTTLES & JARS
Some bottles perfect for beading!

Date: Fri, 4 Jul 1997 10:00:33 -0400 (EDT)

Subject: RE: Are there hand methods for lapidary work?

In a message in LapDigest #17, you write:

<< I don't have lapidary equipment yet and would appreciate information on
hand-working (before electricity) techniques. >>

When I was in grad school, we had to polish our fossil pieces by hand. We
took 1/2 thick plate glass in a 1 x 1 foot section and put our grit and water
on the glass. Then in a Figure 8 motion, we polished the flat sections with
100, 220, 400, 600 grit and then went to a piece of rayon felt impregnated
with cerium oxide. This meant 5 plates of glass. We polished many flat
sections out of the slab saw this way.

Mark Case
Woodmen Summer Camp
Randleman, NC
Subject: RE: Are there hand methods for lapidary work?

Mark: About hand lapping

I have seen this a long time ago, but never done it. How much water? How much grit? What holds the grit on the glass? Can you use something more viscous in place of water to get a better hold on the grit? Are there any special things or problems I should know about before I try this? Finally, why aren't you grinding the glass, too? Hardness of glass is about 5.5, hardness of silicon carbide is 9.25-9.5 (according to Sinkankas).


Date: Fri, 4 Jul 1997 11:48:45 -0700 (PDT)

Subject: RE: Are there hand methods for lapidary work?

On Wed, 2 Jul 1997, Rusty.Etzwiler<> wrote:

<<I am ...(snip)... fabricator. I don't have lapidary equipment yet and
would appreciate information on hand-working (before electricity)
techniques. I have the Lortone hand-cabber but know there must be other
methods that can be done ..(snip).. without electric(ity) ..(snip)..
Any others interested in learning about such techniques?>>

Obviously, a lot of stones were worked before there was electricity.
Pressure-flaking or knapping can certainly be done without it. I've seen
modern arrowheads made from opal, bottle-glass and quartz as well as the
more traditional flint and obsidian. Be sure to wear eye protection and
gloves if you're going to attempt this, however.

Although it is slower than if you were using power tools, carving can be
done with hand abrasive techniques, especially in softer materials. Amber,
soapstone, alabaster, and the calcites can be worked with steel riffler
files, then smoothed out with successive grits of silicon carbide
sandpaper. For harder stones, you can get diamond files and rifflers to do
the roughing out.

A bow-drill can be handy for making holes in beads. These were used
originally as fire-starters, but were soon equipped with stone points and
became the first "power" tools. Mounted horizontally and powered by foot,
they evolved into the first lapidary arbors. Put a modern Jacobs chuck and
a drip-feed on one, and you can use it the same way as a flex-shaft tool,
with the added advantage of being able to hold the work with both hands.

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff

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