Edited and Published by Hale Sweeny
Web Site:
Associate Editors: Geo. Butts, JR Shroeder, Steve Henegar,
Margaret Malm, Sam Todaro, and Ed Elam

This list digest contains the following message subjects:

1. LapDigest News for Issue No. 284 - Sun 2/18/2001
2. NEW: What is "Tambrite-C" Polish Powder?
3. NEW: Need Information on Crystallogical Concepts
4. RE: Heat Treating Agate to Improve Appearance
5. RE: Heat Treating Agate to Improve Appearance
6. RE: Heat Treating Agate to Improve Appearance
7. RE: Heat Treating Agate to Improve Appearance
8. RE: Heat Treating Agate to Improve Appearance
9. RE: Heat Treating Agate to Improve Appearance
10. RE: Heat Treating Agate - a Bibliography
11. RE: Beads: Operating the Covington 5" Bead Mill
12. RE: How to Enhance/Stabilize Turquoise Color
13. BIO: John Cushing
14. FS: 8" Poly Arbor
15. WTB: Morrisonite
16. WTB: A Drilled Hole (Hanging a Heart Shaped Cab)
17. SHOW: June 22-24 in Paso Robles, CA.
18. CLASSES: Chicago Area in Feb/March


Subject: LapDigest News for Issue No. 284 - Sun 2/18/2001

This week, several messages sent to LapDig were outside the
scope of our list. One was on hydraulic forming - a neat
way to form metal objects! Another was an ad for a silver-
smithing video. As it is, we have more than enough messages
within our scope. So we sadly have to say no to these
closely related topics. If you have one like this, I suggest
you send it to the Orchid list, or to, or
post it on either the Lapidary Journal board
( on the rockhounds board

Also, FYI, all messages sent to
with a command on the subject line, e.g.; SUBSCRIBE or
UNSUBSCRIBE, are handled entirely by the computer. I never
see the contents of any of those messages.

Ever want chemicals and can't find them? Then you may be
interested in The Chemistry Store. They sell "common
chemicals, in small packaging, without paying the price for
reagent grade. All products range from USP to Industrial
Grade, as well as tradename raw materials." See their
website at:


Subject: NEW: What is "Tambrite-C" Polish Powder?

I just went to a rock club auction and bought a packet of
polish. It is labeled: "Tambrite-C". Can anyone tell me
what I have and what I should use it for. I hate to use it
all up on agates if it is something special for sapphires
or jade or something.

Thank You,

Rose Alene McArthur
Rose: I have never heard of Tambrite, nor have I ever seen
it in any catalog. I did a 'net search using Google, Alta-
Vista, and several other engines and only found a type of
paper with that name from Russia, and other papers from
Finland and Estonia. No polishing powders. Hopefully some
members can do better than I did!!! hale

Subject: NEW: Need Information on Crystallogical Concepts

Hi all:

I am new to lapidary, so I need all the help I can get.
There are no clubs I can talk to and the closest person I
am aware of to my location is 600 miles away. I live in
Minden, Nevada, a very pretty place.

One of the many things I would like to know is, what do you
mean by "A axis", "B axis", and "C axis", and how do you
tell one from the other.

I recommend you see the self-paced learning unit located at
URL = . It's
title is: Crystallography and Mineral Crystal Systems, and
it will tell you all about axes of crystal systems and many
other things. Our members will probably have better answers
for you. hale

Subject: RE: Heat Treating Agate to Improve Appearance

Firstly, what a joy it is to get the Digest again! Thanks
Hale and all!

Now, on heat treating agate to change its appearance: I have
only heated southern "Lake Superior Agate". These are gravel
pit agates which began their existence in the far, cold
north, and then with the help of glaciers and the
proto-Mississippi River made their way down to Arkansas. Per
a couple of articles in Rock & Gem they can be found as far
south as gravel bars in Louisiana. In any event, by the time
they have spent some millennia enjoying the sun, they lose
their vibrant reds and oranges. The structures are intact,
including some remarkable druzy in open pockets, but the
color has faded to almost uniform light tans and browns.
Heating them restores much of their original vibrancy;
heating them carefully and not too hot does so without
making them become flaky. Sadly, I have been unable to
restore them to the deep, bright reds which are the most
prized by collectors and cutters.

I take a Pyrex baking pan and fill it nearly full with
clean, dry quartz sand. I then nest faded Lake Superiors in
the sand by gently pushing them down until they almost are
touching the glass bottom. This is followed by little mounds
of sand to cover the exposed stone surface. Put the pan(s)
in a cold oven, and set the temperature at 150 degrees F.
Every half hour raise the temperature by 50 degrees until
you have reached the maximum non-broiler setting - usually
500 or 550. After half an hour at that temperature turn the
oven off, and leave it shut until the contents have returned
to room temperature - overnight works fine. Remove the
agates from the baking pan, and wipe them clean of sand, and
they are ready to go! I have cut them, and tumbled them, and
they all have come out just fine. The first time I did it I
had some fracturing which I didn't understand. It turned out
that those agates were relatively "fresh" having been dug
out of a gravel pit only 6 weeks previously, and contained
some free water which made its own exit under heat pressure.

Since that first batch I have avoided this potential problem
by heating them to 150 for at least 2 hours to drive out the
water. A better alternative for those who are in a sunnier
place would be to let them heat in a dry sunny window for a
few days.

Jim Small
Small Wonders
In a follow-up letter with Jim, in talking about the ref. by
Mark (see below), Jim suggested that Lakers have lots of
iron in them and they might do better by holding them at
top end temperature for a longer time. hale

Subject: RE: Heat Treating Agate to Improve Appearance

See: under

I also recommend: "Gemstone Enhancements", by Kurt Nassau
ISBN 0 7506 1797 7. And for the real secrets, read books
on gemstone treatment dating back to Pliny the Elder.

Mark Liccini

Subject: RE: Heat Treating Agate to Improve Appearance

While the details are sketchy, I once saw a Japanese TV
program that was devoted to one agate carver's work. During
this program they showed his heat treating method which I
shall try to outline below. The agates he selected appeared
to be of the gray material from Brazil (though this was not
actually confirmed for the particular piece he was working).

His heat treating equipment was a square sheet-metal lined
pit which had a layer of wood (charcoal?) ashes. The agates
were placed inside with several inches space between each
piece. The spaces were filled with more ashes. A sheet metal
lid was placed on top of the pit, and a charcoal fire built
on it. The video showed him fanning the fire so that it got
very hot, and my wife said that he kept this fire going for
several weeks, and allowed it to cool for at least a week
before opening. The results were a very red agate with some
white areas from which he carved a very nice, lifelike carp.

For those interested in his carving technique. He first
cobbed the piece to rough shape with a small hammer and
chisel, stone held between knees on a leather apron. A
statement was made that he had to work with the stone.
Grinding and polishing were done using loose grit held in
one hand while the other applied the stone to a steel
mandrill. Apparently he had many different shapes of
mandrills. I did not see a diamond saw in use in his shop.

I hope that you find this interesting enough to try a little
heat treating on your own.


Subject: RE: Heat Treating Agate to Improve Appearance

Hi Norm,

I have a friend who used to heat treat Brazilian agate to
enhance the colour. First he would slice the agate into
quarter inch slices and these he would place on a layer of
sand in a tray, when the tray was full of slices, the agate
would be covered with another layer of sand, and so on until
the tray was full, the last layer being sand. At this point
it was placed in an oven and gradually heated over several
hours, the heat being raised about 100°F per hour until he
reached the max his oven would go to, I think from memory,
about 500° to 600°. At this stage it was left for 4-6
hours and then gradually ramped back down at 100°F per hour
until the oven was off.

It was then left in the oven until it all cooled down to
ambient temperature; this is important, as taking the agate
out too soon will cause it to crack.

Some agate would treat perfectly, changing a poor gray or
insipid brown into a beautiful deep red. Other agate which
appeared to be the same did not alter at all, and there did
not seem to be any way to tell which would, and which would
not, change colour.

This is the basic process as explained to me by him, and as
he said at the time some more experimenting could refine it
even further for better results. ie. leaving the agate at
the maximum temp for longer.

Hope this helps some.



Subject: RE: Heat Treating Agate to Improve Appearance

The only agate I know that benefits from heat treating is
carnelian. Some of it will turn a dark burgundy red by
heating. A natural and inexpensive way of treating it is by
placing it in direct sun for a summer.

To do it in an oven, pack the carnelian in an oven proof
container surrounded by cat litter or clean sand. Put the
container in the oven and bring it up to the temperature of
the lowest setting. Leave it 1 hour, then go up 50° F. Leave
it there 1 hour, the go up another 50°F. Continue this until
500°F is reached. After 1 hour at 500°F, turn off the oven
and allow the container, carnelian and sand to cool to room
temperature before opening the oven.

Some carnelian will turn very red but other pieces will not
benefit much. I think putting it on the roof in the sun is
the best way. It is natural, cheap, and environmentally

Chico, CA

Subject: RE: Heat Treating Agate to Improve Appearance

<Hale's note: I wrote to Roger Pabian, asking him some
questions about heat treating agate. This is his response.>


Heat treatment of agates is an area in which I have done
very little research or experimentation. I can pass along a
few results, however. My own work has shown that not every
agate is amenable to heat treatment. Some stones react with
very pleasing results and others do absolutely nothing. I
will categorize them below:

1. Honey agates from glacial tills of Nebraska, Iowa
and Kansas. Plain light yellow to dark yellow agates with
onyx and fortification bands and some without bands. Some
would change to shades resembling Lake Superior agates and
others were not affected. Best results were obtained by
placing the agates in sand and heating them slowly to 550°F
and keeping them at that temperature for about 8 hours.
Allow them to heat and cool slowly.

2. Colorless to yellow agates from Brazil and Uruguay.
The results were the same as above.

3. Colorless to light yellow, translucent agates from
Estacion Moctezuma, Chihuahua, Mexico. Absolutely none
reacted to heating. They all came out of the fire just as
they went in.

Those are the only three examples on which I have some data.
The best results were obtained when the agates were heated
in the absence of air. This probably resulted in the
metallic ions being reduced to more colorful oxidation
states. I have not tried such things as charcoal fires. That
may be worth a try this summer when I'm grilling.

One time my friend John Boellstorff and I were working with
some colorless Brazilian agates and we tried heating the
agate in an oxidizing environment. We boosted the
temperature too quickly and the agate literally became a
pop-agate. Just like popcorn, the agate increased in volume
five or six-fold and came popping out of the oven. The
pattern did not change but the agate became red and white
and was of very low specific gravity. I still have the
pieces around someplace and they fit together to form
somewhat of a slab.

I think that in the agate bibliography there are a couple of
papers that refer to heat treating. When I get this indexed,
they will be easier to find.

Sorry I don't have more information for you. Hope the above

Take care,

Roger K. Pabian

Subject: RE: Heat Treating Agate - a Bibliography

Roger Pabian (above) suggested that there were some papers
on this in his Agate Bibliography; I searched it and found
the following ones:

Graves, E., 1965. Dyeing and heat treating quartz and other
stones. Gems and Minerals, no. 339, p. 39 - 43. Artificial

Kathan, M. L., 1949. Coloring agate. The Mineralogist,
v. 17, no. 10, p. 501-502. Paint backs
-----, 1953. Easy Ways to Color Agate. Lapidary Journal,
1953 Rockhound Buyer's Guide, p. 72.
-----, 1977. Easy ways to color agate with heat and
chemicals. Lapidary Journal, v. 31, no. 4, p. 1048-1049.

Luoma, H. L., 1948. Heat treating Brazilian agate. The
Mineralogist, v. 16, no. 2, p. 104-106.

MacCulloch, J., 1819. Account of the method of colouring
agates. Edinburgh Philosophical Journal, v. I, p. 341-344.

Moore, D. D., 1981. Getting the best color from Brazilian
Agate. Lapidary Journal, v. 35, no. 3, p. 632. heat

Nassau, K., 1985. Miscellaneous Gemstone Treatments Part
II, Gemstone Enhancement. Lapidary journal, v. 39, no. 3,
p. 30-40. Artificial coloring of agates

Randolph, G. C., 1935b. Does strong sunlight deepen the
color of carnelian agate? The Mineralogist, v. 3, no. 3,
p. 17-18. India, Australia, Brazil.

Sassen, R., 1977. Dyeing and heat-treating agate and other
stones. Gems and Minerals, no. 477, p. 34-38.

VanAmringe, E. V., 1936. The artificial coloring of agate.
Rocks and Minerals, v. 11, no. 9, p. 194-195.

I searched on the words: heat, treat and color. There may
be others, but I think this is the majority of them. Also,
a quick search of Rock & Gem article titles found two which
may be of interest; they are:

FEB 1985 Color in the Oven
MAR 1999 Iron - The Quintessential Coloring Agent

I have not seen any of the above articles.


Subject: RE: Beads: Operating the Covington 5" Bead Mill

The following are the operating instructions which come with
each Covington 5" Bead Mill, courtesy of the Covington
Engineering Co. However they should also be broadly
applicable to the operation of an old bead mill set in a
drill press.


The 5" Bead Mill will make beads from 5/16 to 3/4 inches in
diameter. The one-speed mill turns at 380 RPM; the two-speed
mill at 380 and 250 RPM. The fast speed is best suited for
producing beads from hard materials such as agate, jasper
and jade. The slower speed reduces the abrasive action and
should be used when processing softer materials such as
malachite, rhodochrosite and turquoise. Softer gemstone
materials require close attention during the milling process.
REMEMBER: soft materials require light mill head pressure
and finer abrasive grit. Making beads from material softer
than 5 (Mohs Hardness Scale) is difficult because of the
fast abrasive action of the mill.

The bowl and milling head can be quickly removed for easy


Cut the material to be used for making of beads into cubes,
slightly larger than the size of beads desired. Accuracy in
cutting the cubes so they are the same size will produce
more uniform beads. REMEMBER - the largest preform will be
ground to the smallest size, so accuracy of cube size will
hasten grinding. Complete the preforming process by
grinding off all corners and sharp edges until the cube is
a rough sphere.

The preforms must be rough spheres to ensure rotation during
milling and approximately the same size to keep the milling
head level.


Safety: Before starting the unit, read and comply with the
Covington Safety Demand Sheet. CAUTION - remove both 1/2"
collars on outboard vertical rods before starting motor.

Load: Turn the top grooved plate (mill head) upside down and
fill the groove about 80% full of preforms that are about
the same size. This quantity is the load to be placed in
the bowl.

Grit: Place the preformed beads in the bowl with several
tablespoons of silicon carbide grit and enough water to make
a slurry. For agate, jasper and jade 80 grit is recommended.

For softer materials such as malachite, rhodochrosite and
turquoise, start with 220 or 400 grit. Use enough water to
keep the slurry liquid. For hard materials, a second grind
of 400 grit is recommended.

Install grooved plate and let it rest on the mass. Let it
run for a minute. Beads will automatically find the groove.
Remove plate and check load. To provide additional abrasive
action, add l or 2 pound weights to the grooved plate.


Preformed beads should be checked frequently at the start of
milling or at 10 minute intervals. Any broken pieces should
be removed as a bead rolling over broken pieces will break
also. Grit has a tendency to drift into the center of the
bowl. Stir and spread occasionally. When beads are round
and to size, remove from bowl.

For Graduated Beads: First remove one bead when rounded for
center bead in strand, then every few minutes remove two
beads that match in size but are slightly smaller than one
removed previously. The smaller the beads get, the faster
they will grind. DO NOT remove so many beads so the top
grooved plate will not remain level.


Remove bowl and plug ends of hole in bottom to protect
sleeve bearing. Wash bowl in water and scrub with brush to
remove all traces of grit. Wipe bead unit clean of residue
and dust. CAUTION - DO NOT dispose of grit in a sink or
sewer or it will clog the drain.


Place beads back in the bowl with several tablespoons of 600
grit and enough water to make a slurry. Grind and check
frequently, adding water as necessary until the beads are
smooth and ready to polish. DO NOT allow the slurry to
become dry.


Tumble the beads in a small tumbler using cerium oxide
polish. Thin polish with water to a texture of light cream.
Add tumbling media to make an effective load. Take care to
tumble only beads of the same hardness together. Also,
tumble beads before drilling any holes.

Send questions on these procedures to Lapidary Digest. We
will forward them to Dan Drouault, President of Covington
Engineering Corp., and publish his answers here.

In the next issue, we hope to publish a simple method for
making single spherical or tubular beads from a preform
which has been drilled. Then in the following issue will
be a discussion of making spherical marbles or beads from a
cube of lapidary material. hale

Subject: RE: How to Enhance/Stabilize Turquoise Color

A mine in Patagonia, Arizona that will treat turquoise for
color and stability. I believe they charge by the pound.
Phone 520 456-9260 or Fax 520 732-9933 or Email:

Grant Johnston
Chico, CA

Subject: BIO: John Cushing

Hello to everyone. I'm John Cushing from Eugene, Oregon. I
guess that I have been a rockhound for most of my life that
I can remember (58 years), but I didn't get into lapidary
work until about 14 years ago. I have been cutting and
selling cabochons commercially for about ten years. I don't
make a living at this (in real life I'm a machinist), but I
do a real good job of supporting my hobby. And about a year
and a half ago I starting setting some of my stones in
silver for sale on consignment. I also do quite a bit of
repair work (replacing missing stones, repolishing scratched
stones, etc.) for jewelers here in the area.

I do most of my work on a Pixie (a cabochon maker from
Diamond Pacific). I have four saws; 14, 10, 6, and 4 inch.
I do drilling with a Dremel tool mounted in a drill press,
and a small amount of carving with a Fordham flexible shaft
tool. Most of my polishing I do on a small polishing unit
I built myself. And the small amount of flat work I need
done, I do on an "All You Need" flat lap.

I think The Lapidary Digest is an excellent idea. (Many
thanks to you, Hale.) And I look forward to learning from
the many wonderful people that are participating in this

John D. Cushing
Welcome, John! I hope you enjoy the Digest, and hope you
will be active and contribute as possible. hale

Subject: FS: 8" Poly Arbor

Hi -
I have a brand new, never used Poly D14 8" arbor for sale.
I am asking $125 + shipping. The retail value is about $220.
Anyone interested may contact me offlist.

Thank you

Bob Edgar
Yardville, NJ

Subject: WTB: Morrisonite

Does anybody know a source of rough Morrisonite for
faceting ? If so, please contact me directly at the address
shown below.


Subject: WTB: A Drilled Hole (Hanging a Heart Shaped Cab)

If you have a good technique and would be willing to drill
a hole for me in a piece of onyx for a modest price, let me
know. The stone is a gorgeous cab in the shape of a heart
and measures 2X2 inches, cut by myself. My desire is to
have a hole drilled perpendicular to the heart so that I
can wirewrap a bail and hang the piece on a chain as a
pendant for my wife. The area to be drilled is about 3/16
of an inch thick.

If anyone can drill this hole for Steve, please write him
and work it out with him. I suggest, Steve, that you talk
with others who have hung hearts as pendants; there are
several ways to do this - some much more attractive than
others, but this is a subject outside the scope of LapDig. hale

Subject: SHOW: June 22-24 in Paso Robles, CA.

the California Mid-State Fairgrounds in Paso Robles, CA.
Over 150 exhibit cases and special exhibits including
dinosaur egg and other dinosaur items, T-Rex head, a huge
fossil whale vertebrae, petrified wood, Biconoids,
Benitoite, Jade and gorgeous spheres. Demonstrations,
lectures, food, over 40 merchants selling gems, jewelry,
minerals and much more. Youth activities and kids games.
A very educational and fun show for young and old
interested in the Earth's treasurers. For information
telephone (805) 238-4366 E-mail:

Subject: CLASSES: Chicago Area in Feb/March

Hi Everyone,

The West Suburban Lapidary Club (Midwest Federation) of
Elmhurst, Illinois in the Chicago area is offering the
following Lapidary Arts Classes in cooperation with the
Elmhurst Park District:




For those of you in the Chicago area who are interested,
please contact the Elmhurst Park District at 630-993-8989

The classes are staffed by Club Members who are interested
in the craft and wish to pass their knowledge and interest
along to others.

Doug Feistamel
Lapidary School Director
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