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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 139 - Friday 5/1/98
2. Lapidary Clubs in Long Island NY Area
3. NEW: Encrustation of Black Onyx or Corundum
4. RE: How to Tumble Fluorite
5. RE: Using Diamond Abrasives in Tumbling
6. RE: Using Diamond Abrasives in Tumbling
7. RE: Using Diamond Abrasives in Tumbling
8. RE: A Possible Cheap and Safe Cutting Oil
9. RE: Drilling Stones
10. RE: Drilling Stones
11. RE: Drilling Stones
12. Re: Drilling stones
14. RE: Opal Price Guide
15. RE: Opal Price Guide
16. RE: Opal Price Guide
17. FS: Triplet 10x Loupes


Subject: LapDigest News for Issue No. 139 - Friday 5/1/98

Lots of letters in this issue. In putting the issue together,
I was reminded to remind you to:

.. Please add the four words which makes what you say so
useful: "non-commercial republish permission granted".

.. Sign the letters.

.. Spell check your letters.

The following topics are in the hopper for near-future issues:
.. Sphere making (might require two or more issues)
.. Channel Work - I am trying to find a way to put some
channel work patterns on some web page for your use. If
anyone has any patterns they would like to share, please
send me a note telling me this, and then send me xerox
copies for publication to list members.
.. List of "all"(?) Lapidary Books.

If you have any comments about these topics, please send them
to me soon.

I will be away ( late next week, but the
computer will be left running, so Archives will be available
to be accessed. Next issue on Monday.

Have a good weekend, and have fun!!!



Subject: Lapidary Clubs in Long Island NY Area

I recently moved to the Long Island Area in NY. I am
interested in facetting and would like to know if there are
anybody or any rockhound clubs in this area.

Thank you


Subject: NEW: Encrustation of Black Onyx or Corundum

Encrustation is the carving out of a stone to accept a metal
symbol; like a Masons ring or class ring. Sometimes these are
just manufactured all at once as with class rings but others
are carved.

Can anyone tell me if they do or know of somebody who does
this kind of work? I am posting this for a friend and don't
know all the details but he is looking for a source that will
do either one of a kind or small run groups. Today most is
done with an ultrasonic device and this is what my friend is
looking for. It will not be a standard symbol otherwise he
would just buy the cabs with the metal symbol already in
place. The other option is if anyone would know where he
can get the dies made and an appropriate ultrasonic machine
and technical info to do the work himself.


Subject: RE: How to Tumble Fluorite

<<Can anyone tell me how to tumble fluorite and end up with a
polished product? I use a vibratory tumbler.>>

I've had little success in (tumbling fluoride in) rotating
tumblers. Fluorite is just too soft. Like malachite, it
"evaporates" rapidly on coarse grit -- I can't even let it
run one full week, until the grit is gone. And even with
plastic pellets it doesn't take a good shine on a long
polishing run. Possibly with more pellets versus stones, or a
different polish compound - I've used aluminum and cerium
oxides - it would work. It seems the surface is frosted with
tiny collision pits.

Try using pellets or walnut shells or something, and tumble
nothing BUT fluorite? I had it mixed with other "fragile"
stones that needed pellets, but these included feldspar and

I sprayed one tumbled piece with acrylic (cheating, I know),
and after that a friend admired it so much I let her take it
home. :-)

Alan Silverstein

-- non-commercial republish permission granted --

Subject: RE: Using Diamond Abrasives in Tumbling

In response to Hale's note, rather than plating something
would diamond in something like Cratex ( as in wheels ) work?
Or maybe in a resin base like the old "glass ( Dyna? )" laps.

Craig Nielson

Subject: RE: Using Diamond Abrasives in Tumbling

<<a slightly different one is whether one might plate - say,
stainless steel or ceramic beads with diamond of various grit
size, and use these instead of SiC for tumbler processing.
Would it work? Would there be any advantage to this?>>

Count me dubious. Diamond is used for grinding/polishing
because it's harder than SiC, so it cuts faster and lasts
longer. (Any other reasons?) But tumbler grit is relatively
inexpensive, especially considering you can recycle/reuse the
prepolish and polish compounds. (Pour the slurry/rinse water
into a gallon jug, let it settle, pour off the mostly clear
water, shake up what's left, add a little fresh oxide each
time... It works.)

I doubt that diamond (in any shape or form) would be
cost-effective for tumbling; besides, what's the rush? Even
in a vibratory tumbler I'm not sure diamond would cut faster.
And how would you separate the diamond, or diamond-encrusted
metal/ceramic, from the stones after tumbling? Pellets are
enough of a hassle even though they float.

Alan Silverstein

-- non-commercial republish permission granted --

Subject: RE: Using Diamond Abrasives in Tumbling

(See quote in message above for topic)

It might work, but it seems to me that the impacts involved,
especially that where one plated nodule hits another, would
quickly wear out the grinding media in the same way the
ordinary grit wears out. The main reason diamond plated
abrasives last long is that they're used on soft stones.
If the plated media is allowed to tumble with itself, that
advantage is lost.

Nevertheless, this might be a great way for some company to
drastically raise the cost of tumbling to match the needs of
those hobbyists with enormous disposable incomes to blow...

Bottom line to me seems to be that the existing methods work
beautifully, so why mess with em?

Actually though, back to using diamond in tumbling, I do
recall that it can be used in later stages as a dry polish
compound on perhaps crushed walnut shell. Something like
dri-shine only using successive grades of diamond compound on
the dry media instead of the rouge in dri-shine (which is
usually used in tumbling metal, not stones). Seems to me I
recall one vibratory tumbler manufacturer sorta recommended
that technique. I recall a machine with several small open
topped bins, maybe a vibrasonic(?) that was set up that way.
Stones were being tumbled interchangeable with jewelry
findings in that machine, using the dry diamond impregnated
compound... Been long enough ago since I saw that, that I
can't say I recall more...

Hope this helps.

Peter Rowe (Seattle)

non-commercial republish permission granted

Subject: RE: A Possible Cheap and Safe Cutting Oil

In a message dated 98-04-29 14:22:16 EDT, you write:

<< Our Lapidary Club ran about 4 months with Propylene Glycol
antifreeze in an 18" slab saw and found no difference compared
to oil... >>

It is my understanding that antifreeze is a carcinogen. I
would read the warning labels VERY CAREFULLY before using it
in a saw.

Don At Campbell Gemstones
Date: Wed, 29 Apr 1998 15:09:53 -0400
Subject: RE: Drilling Stones

Some months ago, I think there was a question on this very
topic submitted to the digest, and there were several good
responses. I'll bet if you look in the archives you will find
the topic listed there. If I may, I will summarize what I can
remember about the responses.

One way of finding diamond drill bits that are very
inexpensive when you consider how many holes each one will
drill is to contact your local dentist and ask him to let you
look through his catalogs of dental drill bits. There is an
amazing variety of shapes and sizes available, and they come
in grits up to very coarse. Let me tell you, when they say
very coarse, they mean it will drill through the hardest
material in nothing flat. They can be used in dremel tools
or foredom equipment, and you must lubricate the drill bit
with water as you drill.

The great advantage of dental diamond drill bits is that
there is such a great variety of shapes and sizes available.
The other suggestion that was made, and I have to admit I
haven't tried them yet, was to try the triple ripple drill
bits that are offered for sale in a lot of the lapidary
supply catalogs. Apparently, they will also drill quickly
and hold out very well.

Vance McCollum
Earth Relics Company

Subject: RE: Drilling Stones

Drilling a stone can be done with a Foredom using a diamond
bit--and cooling it by drilling in a little water. We use a
custard cup and dip the stone and bit to keep them cool.
Works for us! We drill lapis, chrysoprase and a lot of other
stones this way! Try it--it works!

Phil Magestro

Subject: RE: Drilling Stones

Sounds like you want to drill a hole at least 3/32" (close to
2.5mm). Would recommend a drill stand with handle so that you
can "peck" at the hole. The cheap diamond plated burrs aren't
the way to go, unless you only want to drill one or two. Look
in one of the rock magazines for diamond drills, you might
try some of the web sites too.

The method is simple, build a dam of clay around the place
you want the hole. Add a little water, and using light
pressure feed the bit into the stone for a short time (1 - 3
seconds or so) release the pressure so that the swarf can
clear and repeat until the hole is deep enough. This method
can be used with loose grit and a metal (brass iron?) rod.
Important to keep pressure light, stone secure in fixture.
Note that some recommend drilling 1/2 way thru then turning
the work over and start from the opposite side so that the
holes meet in the middle. This prevents chipping when the
drill breaks thru.


non-commercial republish permission granted

Subject: Re: Drilling stones

Here's my 2 cents but it may only add to the problem. I spent
most of the night drilling three holes in a 3.5mm thick rock.
I used diamond drills, old dentists drills, and the drills
you get at the hardware store when you ask for a little
drill. It was the latter that did the job....finally. But I
went thru two of them.

I have a foredom. I drilled slow and didn't push hard, I
drilled slow and did push...sorta hard, I sped up, I slowed
down. I was in a saucer of water so I could keep things cool,
lubricated, and washed out.

My stone is a green river rock from Indonesia. Not
particularly hard or soft I think.

There has got to be an easier way to do this. Also what shape
drill bit---especially if it is diamond? And how do you get
the hole started if you are using a flat non pointed cylinder
diamond bit?

So many questions......

Thanks all.


non-commercial republish permission granted



I have an abundant supply of polished and unpolished nuggets
(turquoise) to be drilled. I would prefer a hole diameter of
0.060 to 0.125 " or appx 1/16 to 1/8 " . I would like to be
able to drill enough to justify the labor and expense
involved. The question is: what is the going price per hole
of stone drilled? And what is the most economically feasible
way to drill enough stone so as to be a viable economic

" I labor to Love, I don't love to Labor " (SMILE)

Robert L. Powell
(Ed. Note: I would think that this would be dependent on the
cost of the nuggets, the price you may charge for the drilled
stones, and other economic factors which we don't know. A
simple economic analysis should lead to a rough approximation
of the maximum unit drilling price to spend. Then an analysis
of drilling costs should allow you to say if drilling can be
done within the max. drilling cost allowed. hale)

Subject: RE: Opal Price Guide

In a message dated 98-04-29 14:22:16 EDT, you write:

<<"Generally the price per gram is equal to the cost of the
cut stone per carat". Is this a pretty good rule of thumb?
Is this for wholesale or for retail? (the book doesn't

Susan, let us try this. You buy an Ounce (31.1 grams) of
rough opal for $100.00. Out of the ounce, you are going to
find a few stones that have something wrong with them and a
few that are really nice. So figure that you get around 80%
cut table material. Now if your opal is like most, it isn't
broken into shapes that all you have to do is polish. Most
require some shaping and if you are cutting ovals, somewhere
around 30% yield is about the norm, so you should expect
(31.1x0.8x0.3) around 7.5 grams or 37.5 ct of finished opal.
You paid $2.67 per carat for your finished opal. Your rough
cost was $3.22 per gram. So your "COST" will work out close
to the statement, BUT!!!!!!! This is not your price. You
have to figure cutting cost, your time is worth something,
your equipment cost something, the electricity, etc. are
all added to your "cost". Now you need a little profit. You
need to add all of these things together and come up with
your "Price". You will not sell all of your parcel of opal
right away so you need to be able to cover your expected
return with just a few stones. Those are the Killer ones in
the group. The Dogs will be around forever.

So the statement about "cost" is correct as far a material
cost goes but it is not a way to price your stones. Your
supplies, operating expenses, and profit all go to figuring
a price, and then for opal, what does your gut tell you.

Don at Campbell Gemstones

Subject: RE: Opal Price Guide


Downing's opal-pricing methods as described in his book are
excellent. But experience has shown me (as well as others,
apparently) that the prices listed in "The Guide" bear very
little resemblance to those in the marketplace we sell in:
they are a LOT higher, IMHO. But maybe you have a different
market; you have to adjust your pricing to be realistic for
the buyers you hope to attract. Downing's pricing system,
while far from perfect, is a valiant attempt to systematize a
truly mind-boggling problem. If I wore a hat I'd take it off
to him. By and large, opal pricing boils down to experience
and instinct, and Downing has provided at least a framework
to begin from. If you cut a lot of opal you begin to
appreciate how rare truly fine stones are, and develop a
sense for the gradations of value: brightness, pattern,
colors, base potch color, etc., etc.

As for the cost of opal per gram/carat, this is mainly a way
of thinking about comparative values. If you think you might
buy some $500/oz. rough at a show, it's easier to decide
whether you can sell it with your normal mark-ups for labor,
etc. by quickly dividing 30 into 500 and realizing your cost
FOR MATERIAL ONLY will be around $17 per carat (cost per
gram is the same as cost per finished carat, assuming a yield
of 20%, about 30 carats per ounce, -- a figure I've found to
be pretty reliable over the years). Bear in mind there's a
big variable here: all the cut stones from a parcel won't be
of the same size, quality or value, so we're talking about
averages. But I have found this simple formula to be of
enormous help in buying rough.

If you have questions about whether cut stones from a parcel
(as above) will sell for the cost-plus-labor & overhead
figure you arrive at, check around for cut stones at that
price and see how they compare with the rough you're
considering. Figure that most of the prices you'll see are
retail. "Wholesale" is usually extremely variable, depending
on the quantity purchased.

Rick Martin

non-commercial republish permission granted

Subject: RE: Opal Price Guide

I have to agree for the most part with comments already
expressed, however, beauty, expense, effort and presentation
have little to do with value. Pricing anything that contains
some of ones artistic expression is a teeth gnashing and hair
pulling experience at best (I've been doing this a while and
am running out of both).

If your stones are compared to available products a fair
estimation of value is achieved, an independent appraiser can
sometimes do this and the insurance replacement value they use
would be close to double what the stone should fetch. Of
course gut feelings can make a higher or lower asking price.

Dr Downing's works are generalizations as are all text books,
taking that into consideration they are excellent volumes and
quite corrects in content. A specific stone however needs
specific interest to be understood. Rough Stone dealers are
not philanthropists and they price their goods according to
what they believe the yield will be. With opal this doesn't
always work as sometimes the good stuff is hidden: a recent
sale of a fine chunk of Coober Pedy white with extensive
sandstone covering for $1600Can revealed an incredible
harlequin broadflash semi-crystal valued at $50,000Can.

I sincerely recommend you make an appointment with a local
appraiser or two and take a few of your stones that cover the
range of what you own, your own master set as it where. DO
NOT bother with written appraisals, but listen carefully and
take notes. I guarantee it will be the most useful 20 bucks
you've parted with in a long time.

Anthony L. Lloyd-Rees
web site:

non-commercial republish permission granted

Subject: FS: Triplet 10x Loupes

I have just imported from Belarus (former Soviet Union) a
high quality, low cost triplet 10x loupe. An image can be
found on my website at

I invite individuals, dealers, educators, and clubs to
contact me for additional information.

Yale Goldman

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