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. 163 - Sat 8/8/98
2. RE: Nephrite vs Asbestos
3. RE: Nephrite vs Asbestos
4. RE: Mixing Saw Oils
5. RE: About Charoite - Pricing
6. RE: About Charoite - Cutting Advice
7. RE: Filling Pits in Cabs
8. RE: Filling Pits in Cabs
9. SHOW: Chatham County Swap (North Carolina)


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<MSG1>

Subject: LapDigest News for Issue No. 163 - Sat 8/8/98


Venkat Ramvi (ramviv@hotmail.com) wrote asking the list if
any of us knows of rock clubs in the San Francisco bay area.
If so, please write him with details such as who, when and
where.

It is August - where the hell did the year go? - and almost
back to school days. Make sure you get those field trips in
before the cold weather sets in ... As my friend BOO says:
"A weekend without a field trip is like Thanksgiving without
pizza!" Have fun, gang!

hale
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<MSG2>

Subject: RE: Nephrite vs Asbestos


<<But remember the largest source of silica fibers most of
us are exposed to, all day, every day, is house dust.>>

Yeah, but, there was a brief article in Science News a few
years ago (sorry, no reference handy) reporting on research
that showed "fresh" silica dust is more dangerous than "old"
dust (60+ days). Apparently freshly broken surfaces are
more likely to act like free radicals(?).

The moral is, age your lapidary dust well before you inhale
it. :-)

Alan Silverstein
ajs@hpfcajs.fc.hp.com
(non-commercial reprint permission granted)
-------------------------------------------------------------
(Note: You have a good memory, Alan. The following is taken
from the Archives file named: <DangersOfRockDust.txt>:

<<In an earlier post on Rocks-and-Fossils mail list, dated
7/16/97, someone had suggested that there were two reasons
why freshly cut rock dust was far more dangerous then wind-
blown dust. First, it has sharper edges which can really
damage your lungs; the comparison between them was compared
to the differences between shards of broken glass and
tumbled pebbles. Next, the concentration of rock saw dust
is probably much greater than the concentration of dust in
wind>>

Nathan Schachtman <nschacht@voicenet.com> touched on this in
his reply to an earlier note. Nathan wrote:

<<The reason is much more likely to be that freshly fractured
silica carries a surface charge (high zeta potential) that
makes the particles much more membranolytic or cytotoxic. It
really has nothing to do with the shape of the particle.

If you take those same particles and allow them to age, their
biological activity goes down as the surfaces are hydrated.
The toxicity of the particles can be restored by washing the
particles in acid to dissolve away the layer of hydration
(Beilby layer) and expose the fresh silica surface.>> hale)
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<MSG3>

Subject: RE: Nephrite vs Asbestos


Great article, Dick! I was really worrying about this one,
since I was just about to start grinding on some California
Jade. Is there any possibility hat this jade might be
contaminated with asbestos fibers, like the soapstone here
is? I'd hate to be spraying asbestos around the place. While
asbestos may be less immediately toxic than silica, I've heard
that the toxicity of freshly ground silica is moderated over
time by humidity, but the asbestos fibers just linger. Any
comment? We were kicking this around a hundred or so issues
back...

I'd like to put this article up on my page (I'm thinking of
starting a stone section)- is that alright with you? And are
there any more at home like her?

You wrote:
<<.... it helps to keep the problems straight. Nephrite is
NOT asbestos. The confusion arises from the fact that
nephrite IS the same chemical composition as one of the
forms of asbestos (Actinolite). The characteristic of
asbestos that cause trouble is its ability to easily break
into fine fibers that are too small to be seen by the human
eye. ...Unfortunately, there are real hazards associated with
almost everything we do, the problem is trying to get correct
information to be able to make informed decisions about what
level of risk we are willing to accept.>>

Andrew Werby - United Artworks
drewid@lanminds.com
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com
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<MSG4>

Subject: RE: Mixing Saw Oils

A handy trick I learned was to take a new vacuum cleaner bag
and use that to filter saw oil. The vertical types work
better. Just hang it over a clean bucket and in a day or so,
you'll have clean oil.

Giovanna Fregni
kfletcher@citilink.com
non-commercial republish permission granted
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<MSG5>

Subject: RE: About Charoite - Pricing

I have collected the following prices for charoite from the
Net and from magazines. Since there is no standard grading
system in wide use, we just have to put the prices out there
and guess as to the quality.

Bridget Easley at White Nights uses the grading system quoted
earlier and shown below, and sold her charoite as follows:

AAA -- $250/lb Rare; dense, fine-grained bright purple or
highly chatoyant.
AA -- $65/lb Exceptional material, w/- bright color and/or
streaks of chatoyancy. Up to 10% inclusions.
A -- $45/lb Average material most often seen for sale;
good purple material with < 25% inclusions.
This grade is often most stable for cutting.
B -- $25/lb Material similar to A, but has faded somewhat
in color or has obvious fractures. Best for
beginning charoite cutters.

Other prices are:

New Era Gems (July '98) $60/lb
On-Line Dealer1(Aug '98) $56/lb
On-Line Dealer2 " $49/lb

hale
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<MSG6>

Subject: RE: About Charoite - Cutting Advice


When Craig Neilson heard that I was about to cut my first
charoite cab, he kindly sent me the following advice:

<<Just keep in mind when cutting that the stuff likes to
splinter on the edges. The worst things that you will run
into are that and the stones' desire to grab a hold of the
wheel surface, more so on the Novas. The stuff also likes to
heat scorch on the surface. I found that doing a slightly
rounded edge ( avoiding all sharp angles at all times during
cutting ) seems to help alot. Also using well balanced
wheels to avoid cutting impact also helped. I also found on
some of the nastier ones that switching to worn SC drums
worked well.

At first start your roughing out on a lighter grit than
normal. At least until you get the feel of the stone.

Sized MM stones are the worst, but still not that bad if
you keep your touch light. My best cab so far is over
50 MM.

Have Fun and happy cutting. The end results are well
worth the time.

Craig & Sue>>

This is right in line with other advice we have received.
Bridget Easley says that her cutters tell her that they use
epoxy generously along the edges as they cut; she will get
details from her cutters and will send them to the Digest.
Does anyone else epoxy the edges before they cut?

hale
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<MSG7>

Subject: RE: Filling Pits in Cabs


Derek

Try cutting with a 600 Nova, filling (with epoxy) and then
going to a well worn 600 wet and dry belt (like on a drum
sander) using a lite touch and a lot of water. Skip the 1200
Nova and go for the polish.

Craig Nielson
cnielson@webtv.net
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<MSG8>

Subject: RE: Filling Pits in Cabs


<< I have tried filling the pits with both Opticon and 330
Epoxy between the 600 and 1200 grit sanding stage (Nova
wheels). The problem is that the epoxy will undercut
every time.>>


I think we have here not only a technical question, but an
ethical one. Is it really okay to fill pits in stones with
glue? I always thought this was something of a no-no. Is it
alright if you disclose it? Is all fair in love and lapidary?

As for the right glue to use, try cyanoacrylate (superglue).
It polishes out a lot better than epoxy. I have used this
myself, when trying to cut a stone around one of those
(rutile?) stars one finds in charoite. They are so stringy
and ill-adhered that something like that was necessary to
keep the needles from peeling out during polishing. Aside
from that, though, the material seemed fairly cohesive. I'm
surprised by the description in the last issue:

<<The main reason it's so rare is, well, it falls apart
when cut. Probably takes one pound of material just to get
one good cab.>>

I wonder if this batch was mined with dynamite? Sometimes
this will shock a delicate material and cause internal
fracturing.

Andrew Werby - United Artworks
drewid@lanminds.com
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com
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<MSG9>

Subject: SHOW: Chatham County Swap (North Carolina)

(Note: Usually I won't run show ads this long, but, hey, it's
our next-door-neighbor club and I always enjoy this show, and
we are have only a few items this issue. So I'll take my
prerogatives and run it!)


Hi everyone,

I wanted to invite everyone to visit the Chatham County North
Carolina Swap on August 22 and 23. The directions are fairly
simple: Go to Pittsboro, NC. Pittsboro is located in the
middle of the state on US 64. From Raleigh, go west on US 64.
>From Greensboro, go south on US 421 to US 64 and then east.
>From Charlotte go north on HWY 49 to US 64 and then go east.
(Consult your map for directions from more places.)

When you get to downtown Pittsboro (one of those really cool
circle town squares!) go east on US 64 about 3 blocks or so.
On the right side (before you get to Food Lion!) take a right
on Fairground Road. The Chatham County fairgrounds is on the
left about 2 blocks. It is kind of a small place.

Dealers will be set up both inside and outside. I will be
inside. New stuff for me is sugilite slab rough and neon
apatite facet rough. In minerals, I have some great new
quartz on pyrite from Peru and a killer piece of fluorite
with strontianite covering some of the cubes from Mexico.

For North Carolina mineral collectors, I understand that Rob
Whaley will be set up with his TN and SCAB materials. VERY
NICE STUFF!

If you need some collecting materials, Ed Deckert (a member
of my club) will be set up with items like grits, fold up
boxes, cleaning supplies, lapidary tools and more.

Come on by, snag a cup of coffee and chew the fat, tell some
stories and listen to my lies. We had a great time in Spruce
Pine. Sorry if we missed you.

Mark Case
MarkCase@aol.com
Randleman, NC
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