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. 288 - Fri 3/16/2001
2. NEW: Tumbling Times and Concentrations
3. NEW: How Do You Cut an Egg Shape?
4. NEW: Cups for Polishing Jade Spheres
5. RE: Heat Treating Agate to Improve Appearance
6. RE: Druzy Backing
7. RE: Druzy Backing
8. RE: Information on Shahuckite (or Shattuckite?)
9. RE: Need Tips on Working Black Coral
10. RE: Need Tips on Working Black Coral
11. RE: WTB: Slab/Trim Saw
12. WTB: Opal
13. SHOW: Charleston, SC on 5, 6 May 2001


Subject: LapDigest News for Issue No. 288 - Fri 3/16/2001

I'm asking for your help. Please send or give the following
note to your club bulletin Editor for inclusion in your club

"The Lapidary Digest is a widely-circulated e-mail Digest
devoted to queries and answers on Lapidary topics. Delivered
weekly. Subscription is free; just send an e-mail
to and put the word SUBSCRIBE on
the Subject line of the message form."

And remind your Editor that items in the Digest may be
freely published in non-commercial club newsletters without
asking for copyright release for every item. But this
permission also requires that the Editor cite the Digest
and Issue number as the source and credit the authors for
each item published.


If this issue looks a little sparse, it might be because a
query on how to work charoite was pulled at the last minute
by the submitter, who wrote: "Hale, forget this one; if I
had done my research, I would have found what I need in the
Archives." And that is true for a lot of the queries. The
Archives, found in the website,
contain every issue published and have a finding aid (file
of titles) and a search engine. So if you have a new topic,
before you send in a query, spend a little time looking
first in the Archives -- there are over 3200 items from
past issues there! Lots of good info from our members!!

We have talked, from time to time, about building your own
lapidary equipment. There were three books with directions
for building several pieces, discussed in the last two
issues. Now I find a website with similar instructions for
sale: If any of
you have ever bought any of those (or other lapidary
equipment) plans, please write and tell everyone what you
think of them.

It is beautiful outside - at least here in North Carolina -
so take your family with you when you go rockhunting this
weekend. They may enjoy it too. In any even, tell them
and others you love that you do love them. You can't say
this often enough!!!

Till next week ...


Subject: NEW: Tumbling Times and Concentrations

After a long time away from lapidary work, we're
experiencing a renewal of interest; cleaning up equipment
to start using again, attending shows, looking at old books
we have, and finding out what resources are available on
the Web, including Lapidary Digest.

One problem pops up immediately; the concentrations and
tumbling times for a rotary tumbler with different loads of
rocks which may vary from Mho = 5 to jaspers or agates!

Can you point us in a good direction?

Also, any advice about using the same tumbler for polishing
metalwork with wood or steel shot?

Carol & Paul Antrim

Subject: NEW: How Do You Cut an Egg Shape?

I would like to know how to cut and polish an egg shape.
For those people who cut them professionally, do they use
special machinery? Special jigs or fixtures? Is special
machinery necessary for making only one or two eggs?

If anyone knows how to do it 'by hand', please let me know.
And if anyone knows how they make them 'professionally',
I'd like to know that, too!


Subject: NEW: Cups for Polishing Jade Spheres

Hi All

After reading the post on jade polishing, I am wondering if
any of you have any thoughts on building wooden cups for
polishing jade spheres. What is the best type of wood? What
cup depth do you suggest? Have any of you ever given this a
try? Any types of cups that may work better?


Craig Nielson

Subject: RE: Heat Treating Agate to Improve Appearance

Hi Hale,

The entire discussion so far has been based on heat treating
agate to oxidize the iron that is already in the stone. It
is quite possible to add iron oxide (rust, if you will) to
many varieties of agate that do not already contain enough
to enhance the color.

1. Begin with a stone that is rough ground close to final
shape, or a slab, as penetration may be limited.

2. Heat it to about 150 to 175 degrees F in a sand bath
(covered) and hold for a couple of hours. Caution,
the sand is hot!

3. Turn off the oven and let the stone cool in the oven.

4. Make up a solution of iron oxide in water, otherwise
known as rust. If you have access to reagent grade
chemicals, crush up some iron oxide and saturate a
glass jar with as much as will dissolve. Otherwise,
add some iron powder to some water and let it set in
the sun for a few weeks. Anything iron will work,
but the more surface area the better. You should end
up with a dark reddish brown solution, with rusty
clumps on the bottom.

5. Don't touch the stone with your fingers!

6. Put your stone in the solution and heat it slowly to a
low rolling boil. Cover it and let it cool down. Repeat once
a day for a week or so.

7. Let it sit in the solution for another week at least.

8. Repeat step 2 to dry the stone out. It should have a
definite rusty look if the agate was sufficiently porous.

9. Once the stone is dry increase the temperature to about
250 for at least an hour.

10. Next, increase the temperature to around 500 for a
couple of hours.

11. Turn off the oven and let it cool down by itself. This
will take awhile, but the stone is likely to fracture if it
cools too fast.

The more iron oxide you can get into the stone, the better
the color.

Bob Braun

Subject: RE: Druzy Backing

<<The backs of all the stones look the same, a smooth
brownish black perhaps 2mm thick coating. What is that ?
Is it durable, will it withstand water?>>

I would need to see the backing; you can send me a close-up
jpeg, to be sure. But it is common practice to irradiate
Druzy Quartz with very low dosage Cobalt 60 irradiation to
turn them black. Given the typical low dosage, 0.5-1.5
megarads, you may not have full penetration, so it gives the
impression of a coating. You could also get the effect of
the same Black coating, and in this case it would only be a
coating, by soaking or painting the crystals with sugar
paste, or honey and then soaking the geode in a warm
solution of Sulfuric acid. This would burn them black.

Mark Liccini

Subject: RE: Druzy Backing

Dear Helene,

Yes Druzy is wonderful in jewelry, and especially, as you
guessed, in pins, pendants and earrings. What many people
do (me included) is to form a bezel exactly conforming to
stone out of 22kYG bezel stock, then solder this to 14K
backing material, and use 18K accents as needed.

The 22k bezel stock is dark enough gold to really give give
a punch, and because of its softness its easy to bend enough
to hold in the stone. Then add a small cab or tube set
faceted stone with a commercial tube setting as an accent.
(so easy.) If you choose your colors and shapes cleverly and
a add a little detailing with the gold, it looks like a
million bucks.

Feel free to contact me off line, if I can be of any help.
Good luck!

Gary Strickland, GJG

Subject: RE: Information on Shahuckite (or Shattuckite?)

When I checked my Pocket Guide to Rocks and Minerals, my
first observation is that the color stone that I have
matches the Shattuckite in the book. It tested at 3 1/2 to
4 hardness with a reflective index of 1.75. It is not even
close to the paler blue of Chrysocolla which has a hardness
of about 2.

It is possible that it exists in yet unknown locations?

Toni Costonie
Toni: I checked my Mineral Database and found the following
characteristics of Shattuckite, for the record:

Mineral: Shattuckite
Formula: Cu5(SiO3)4(OH)2
System: Orthorhombic
Color: Blue to dark blue
Opacity: Translucent
Luster: Vitreous to silky
Streak: Pale blue
Hardness: 3.5 to 3.5
Density: 4.11 to 4.11
Cleavages: 2
Description: {010} and {100} excellent
Habit: Crystals slender prismatic, 1-2 mm,
radiating spherulitic aggregates; massive,
compact, granular, fibrous
Type Locality: Shattuck Mine, Bisbee, Cochise Co., AZ, USA
Strunz Class: VIIID 04 (Nickel & Nichols) or 9.DE.4

Web references:

There is a photo of a specimen from Katanga, in the Congo,
in the second web reference, above. This confirms that it
occurs in Africa.

Subject: RE: Need Tips on Working Black Coral

Treat black coral like a wood, using a flex shaft and steel
burrs. Finish with Zam or bobbing compound and final White
Rouge. The prior will cut too, you can finish right from the
steel burr marks, but allow for removal of material.

The only trick with Black Coral is the concentric growth
rings. If you carve into them, your finished object can have
the appearance of a crack.

Here is a great link list to
research the Fish and Game Regulations:

Mark Liccini

Subject: RE: Need Tips on Working Black Coral

(Note: Someone sent in a note on this topic which was lost
in editing. I have reconstructed its contents and added to
them just as I had done on the original. Unfortunately, I
forgot who sent it. I apologize to the sender.)

Information on black coral was contained in three articles
published in Lapidary Journal last August, September and
December (2000). They were all by our member Don Dietz
( They are a great reading and tell
about black coral and how to work it. They are:
Beach Gems, August, page 32
Black Coral Beads, December, page 64
Black Coral Jewelry Set I, August, page 62
Black Coral Jewelry Set II, September 72

In addition, the LJ Index lists other articles on Black
Coral in past issues; the notation following the title
refers to the year, month, and initial page. Thus 81:01:2280
means 1981, January (first month), page 2280. They are:

The Black Coral of Cozumel, 81:01:2280
Lapidary Use of Black Coral, 81:04:142
Shaping Black Coral Bracelets, 73:06:558
Introduction to Black Coral, 82:11:1378
Cheju Island and Black Coral, 70:05:398
Cutting & Polishing Hawaiian Black Coral,65:07:494
More About Florida Black Coral, 73:05:416
Hawaiian Black Coral, 62:04:4
The Hawaiian Black Coral Story I, 62:07:388
The Hawaiian Black Coral Story II, 62:08:490

You can get Xerox copies of past articles from LJ. When you
find a paper you want, you may order a copy from LJ for $2
each and $0.50 postage for each 5 reprints. (I think this
price is right, but you'd better check with them. Their
toll free number is 1-800-676-GEMS, and their e-mail address
is They accept major credit
cards in payment. The last batch of reprints I ordered took
only 10 days to arrive. Not bad!

While not as good as having the magazines, you may buy the
Lapidary Journal Index, 1947 -1991, an index of all the
papers published in the Lapidary Journal (LJ) from 1947
through 1991. The contents are organized in several ways
for convenient searching. First, all articles are indexed
by subject. Next, they are indexed by geographical location.
Finally, they are indexed by author. It is a basic reference
for the lapidary.


Subject: RE: WTB: Slab/Trim Saw

Hi Becca

Saw your request for a slab saw. I've been looking for one
too, and ran across a recommendation from some lapidary web
site saying that a plain old tile saw would work just fine
as long as you weren't cutting expensive gem material. I
looked around and found a few saws at some very good prices
(see links below). They are diamond, cooled with water
(a real plus) and seem like they would work very well with
rough up to 3 1/2" deep...

QEP, cheaper unit - I think I'm going to try this one,
might have to figure out how to mount a vise but at the
price it's a whole lot cheaper than the lapidary units. - MK Diamond,
more expensive Anyone have any opinions on this?



Subject: WTB: Opal

Need some ideas on where to purchase some medium quality
150-250 per ounce opal. Any suggestions ?

Subject: SHOW: Charleston, SC on 5, 6 May 2001

The Lowcountry Gem and Mineral Society, Inc. of Charleston,
South Carolina, is hosting its Annual Lowcountry Jewelry,
Gem, Mineral and Fossil Show.

The theme is "Art by Nature", and will be a component of the
North Charleston Arts Festival. The show features free
parking and admission, and will be held on the 5th and 6th
of May, 2001.

The show will be held at the North Charleston Performing
Arts and Convention Center Complex, North Charleston, South
Carolina on Saturday, May 5th, from 10 am. to 6 pm. and
Sunday, May 6th, from 10 am. to 5 PM.

Our dealers provide a wide spectrum of Jewelry, Gem rough,
Collector Minerals, Fossils and MUCH more. Club members
will provide lapidary demonstrations along with Jewelry and
Mineral Exhibits.

For more information, call Ken or Barbara Brennerman at
(843) 556-3127 or John Huck at .

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