LAPIDARY DIGEST
Administered by Hale Sweeny (hale2@mindspring.com)
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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 89 - Tues 12/2/97
2. RE: Lapidary Glues and Cements
3. RE: Lapidary Glues and Cements
4. RE: Retensioning & Straightening Saw Blades
5. RE: Breaking Glassy Rocks for Tumbling
6. SCHOOLS: Baltimore, MD
7. NOTE: Country of Origin
8. WTB: Agatized Coral
9. WTS: Shattuckite


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<MSG1>

Subject: LapDigest News for Issue No. 89 - Tues 12/2/97

In the last issue, Lester wrote saying that his club wanted
to refurbish their Star Diamond VL-16. Unfortunately, I
accidently (stupidly) erased his e-mail address. Lester, I'd
appreciate it if you would send me your e-mail address; I
have some info for you.

The past several issues have included articles concerning
retensioning sawblades. I'm happy to say that we now have a
how-to-do-it article on that topic in this issue.

Carolyn Weinberger sent in a note on the lapidary classes put
on by their club in Baltimore. This is a good example; if we
all submit info on classes in lapidary near our homes, we
will soon build up a good list of classes everywhere!

Be careful in the lap shop; stay safe, but have fun!

hale
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<MSG2>

Subject: RE: Lapidary Glues and Cements


Thom Lane wrote:
<<I used to use the Loctite product ...(snip)...I needed
a product that I could vacuum induce into fine cracks in
opaque materials...(snip)...>>


I've used a product called Opticon for this purpose. I
believe it was an epoxy, consisting of a fluid and a
hardener. The rock was heated somewhat to increase
penetration, then the fluid was applied to the surface and
allowed to sit awhile. (I never tried it with vacuum;
capillary action seemed sufficient.) After this, the excess
was wiped off and the hardener wiped on, allowing it to cure
from the outside in. It was intended for use on finished or
nearly-finished stones, so if the material never set in the
depths of the cracks it didn't really matter. If you use it,
be careful to avoid skin contact with the resin or hardener,
as all epoxies will induce an allergic reaction.

<<Hunt's examples were all with materials through which
light could pass, as were the ones cited by >Marshall Snapp
in Issue 87 (opal triplets).>>

P.S.: Where is Henry Hunt's new book available? I enjoyed
his "Lapidary Carving for Creative Jewelry".

Andrew Werby - United Artworks
drewid@lanminds.com
Sculpture, Jewelry, and Other Art Stuff
http://users.lanminds.com/~drewid
-------------------------------------------------------------
(Ed.Note:Andrew, I recently bought a copy of Hunt's "American
Lapidary: Designing the Carved Gemstone" from Berg's Rockshop
(one of my favorites) for $25 plus postage. Jan Berg's e-mail
address is <janberg@pressenter.com>. hale)
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<MSG3>

Subject: RE: Lapidary Glues and Cements


If the purpose of vacuming the cement into the crack is to
make it invisable then I don't see why the cement would have
to harden in the center. Seems to me it would harden as deep
as the uv penetrated and that would be all that would be
required unless the stone was in danger of breaking apart.
With opticon fracture sealer the resin is applied and the
stone is baked several hours to draw it into the fracture,
then the hardner is applied.I doubt that the hardner
penetrates far enough to make it set up in the center.

Don, the ramblin rockhound
rawhide@webtv.net

non-commercial reprint permission granted
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<MSG4>

Subject: RE: Retensioning & Straightening Saw Blades


Hi folks,

I've retensioned/straightened about three blades so far, two
for a friend and one of my own. The biggest was 10". The
others 8".

Somewhere I'd read how it was done and still had some faint
memory of the procedure. But it was pretty faint. So I went
at the problem by considering how a metal dish is formed in
the first place.

Try hitting a small piece of soft metal on an anvil, say a
button of soft solder or lead. After you've hit it it's
thinner but bigger, it expands outward, there's less of it
vertically but more of it horizontally. Now if that single
button of metal were constrained by more metal all around, in
other words, if it were just one area within a larger sheet
of metal, that extra horizontal extension would want to go
somewhere but it would be hindered from doing so by the
unhammered metal all around it. And yet it's gotta go
somewhere, so it will start to bowl outward. If I'm
hammering a flat disk of copper or silver into a dish I'll
start hammering at the centre, stretching the metal and
making it thinner; it promptly bumps outward and you have the
beginning of a bowl. You make the bowl deeper by repeating
the process.

In a dished blade you already have a bowl. The dish shape
alone indicates that the metal at the centre has been
stretched. Once stretched, constrained by the less deformed
periphery, it has thrust up into the dish shape. Since you
can't "unthin" the centre, the obvious thing to do is
relieve the constraint, and that entails making the periphery
bigger, stretching it, in order to, so to speak, give more
"room" for the centre part.

So, looking at un-dishing as bowlmaking in reverse, I
hammered the blade, round and round and round, working from
the outside toward the centre, with more and heavier hammer
blows applied around the outer section, and constantly
checking progress with a straight edge across the blade. It
worked. The dish gradually became flatter and flatter, such
that the blades cut again. Obviously they're no longer
perfectly like-new flat. But they do cut. And if they dish
again (which they haven't so far) I'll just repeat the
treatment.

Cheers
Hans Durstling
Snowbound in Moncton, Canada
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Subject: RE: Breaking Glassy Rocks for Tumbling


Dan Otcherre wrote:
<<I am not sure if this topic has been dealt with before. I
am looking for techniques, advice on minimizing cracks when
breaking larger rocks for use in rotary tumblers. I have
been working with Amethyst and conglomerates>>


If you are dealing with Amethyst on Geodes matrix(plates)the
best way is to fill a bucket with sand and lay the specimen
Crystals down in the sand.Then a few quick cracks with a
hammer,and off come all the crystals,and the flying debris is
minimized.If you are dealing with a lot of small Crystals it
is easier to pick them out after if you line the bucket with
a plastic trash can bag on top of the sand.

If you want to get into some precision breaking,use German
carbide tipped cobbing hammers.These are nicknamed "German
Knives" for good reason.The chisel ends are inlaid with
carbide and last forever.Coupled with a "V" block.That is a
square piece of <underline>tempered</underline> steel,mounted
so one edge is up,stones will split exactly where you want
them to.In Germany they cast a lead mounting base for the "V"
block.But just as sturdy is a wooden mounting frame with a"V"
groove.If you observe you can rotate the square steel rod,
using all four corners for quite a while before the
resharpening is needed.

You can find a scrap piece of steel of this sort at any
construction site or machine shop.If you rest the stone on
the "V" and crack it sharply exactly opposite,it will split
like it was on cleavage.You can further improve this process
by using a diamond saw to cut a small notch on both sides,
resting the one side notch in the "V".With this method you
can even split stones like Topaz against the cleavage.

You can obtain these hammers in several hardware stores in
the Gem cutting center of Idar-Oberstein,Germany. My company
also stocks them.They come in chisel ends in 5,10 & 20mm
widths.This still is wanting when you need to do a large
break,so the addition of a Eastwig rock hammer is good to
break the larger pieces down.

If you are into mass production,and precision is not a factor
there are commercial pneumatic rock crushers.They work very
well to break a large boulder into pebbles.

Mark Liccini

LICCINI
http:www.LICCINI.com 107C.Columbus Dr.#1A
E-mail:Mark@LICCINI.com Jersey City,N.J.07302
Phone/Fax:201-333-6332
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<MSG6>

Subject: SCHOOLS: Baltimore, MD


Gem Cutters Guild of Baltimore Lapidary classes.
For information: contact Steve Weinberger, by e-mail at:
<cweinber@mail.bcpl.lib.md.us>

Our classes run anywhere from 5 to 10 weeks. Sessions are 2
hours per evening and currently cost $75 for 5 weeks. Number
is limited to 8 students/class.

We also teach faceting - classes are Saturday mornings and
run 3 hours. Cost is $250 Class size limited to 4.

We also teach a variety of jewelry classes, but that's
another topic altogether.

Carolyn Weinberger
<cweinber@mail.bcpl.lib.md.us>
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(Ed. Note: This is a good example of a school posting. It has
a contact person, location, brief description - enough to let
someone who lived near Baltimore know about the possibility
of local lapidary classes. If you have classes near you,
please send in a similar notice about your classes. hale)
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Subject: NOTE: Country of Origin


Hi

My e-mail address "sg2788@brunnet.net" makes it impossible
to determine from what country I am from.

For your statistics I am from Canada, specifically from
Fredericton,NB.

......Leo Doucet......
sg2788@brunnet.net
-------------------------------------------------------------
(Ed. Note: Leo, thanks for your note. We have several members
from Canada who also have 'net' extensions, and there may be
others from other countries as well. I know the numbers are
wrong, for this reason, but I published the list to show the
variety of countries from which we know our members come.
hale.)
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Subject: WTB: Agatized Coral


I was wondering if any of the list members could help me find
a source for tumble polished agatized coral. I suspect it
would have to come from someone in Florida, where the coral
is found. I need pieces that are in the 3/4 to 2" size, to
use as jewelry pendants. I might also be interested in
trading for such material, if that would help.
Thanks,
Vance Mccollum
erelics@dycon.com
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Subject: WTS: Shattuckite


We have for sale....
Shattuckite, Secondary copper mineral, Shattuck Mine, Bisbee,
Arizona, Simliar in color to that of azurite, makes nice
cabochons and carvings... Available till supplies are gone at
$35.00 per pound , We will get as close to your order as
sizes will allow...
Thanks
cj

Gemstone Brokerage Associates Ltd. Telephone (518)438-5487
P.O. Box 8930 Albany, N.Y. 12208
http://www.24carat.net/gba
Http://www.sweet-sites.com/gba cj-gba@worldnet.att.net
SUBSCRIBE TO OUR EMAIL LIST OF & CAB ROUGH GEMSTONES
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