LAPIDARY ARTS and FACETERS DIGEST
Issue No. 247 - Monday, November 17, 2003
Moderated by: Thurmond Moore III
Committed to carrying on the fine works of
Hale Sweeny and Jerry Dewbre
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Index to Today's Digest
01 NEW: excerpt from the 2nd edition of "The Gem Merchant
02 RE: sapphires polishing
03 RE: Followup on sander
04 RE: CA Fires
05 NEW: Big sapphires!
Subject: Re: Issue No. 246 - Friday, November 14, 2003
Date: Fri, 14 Nov 2003 18:48:22 -0300
To: LapidaryArtsDigest <firstname.lastname@example.org>
From: David Stanley <email@example.com>
Dear fellow readers,
Below find an excerpt from the 2nd edition of "The Gem
Merchant-How to be one-How to deal with one." I hope that it is
informative and perhaps entertaining. If you want more information about
the book, or wish to order the easiest way would be to go to
www.gembuying.com an click on the link for more information.
HOW TO GRADE AND VALUE
Once you are prepared and want to assume the work of a cutter, there are some
basic rules you should remember when analyzing rough. When we say "ready,"
we don't mean that you have faceted a few stones. We mean you have sawed and
formed enough of the type of material you will be working with to have a good
idea of what gems come out of what rough and how.
We have to know how we are going (or know how we will order others) to
saw, grind, polish and how to retrieve what size, shape, weight, tone, etc. Now,
since you already know how much the cut stone is worth, you can calculate the
worth of the rough by subtracting your profit margin, cutting costs, and the
percentage to compensate for the cutting risks (breakage, appearance of
inclusions, etc.) from the selling price of the cut stone. Never evaluate rough
exclusively by weight. There may be a wonderful little gem in the corner, so
evaluate only on the basis of the gem that will be recovered.
When analyzing rough you want to use oil, if possible, to make the inside of
the crystal clearer. This oil (preferably refractive index liquid) is spread on the
surface of the rough, or the rough is placed in an immersion cell with the liquid in
the cell. At the mines we usually don't have immersion cells, so we spread the oil
on with our fingers. When we hold the rough to the light, the light should shine
strongly into the stone but not directly in our eyes. Placing the rough directly
under the edge of an incandescent lamp shade usually accomplishes this.
Try to examine rough against a white background in order to avoid color
contamination when you are judging. Black is preferred with light to medium tone
aquamarine in order to highlight the inclusions. You may want to pass your hand,
or another background, under the stone momentarily to contrast inclusions which
would otherwise not be noticed.
It is most important to view a stone from three dimensions, usually the "A,"
the "B" and the "C" crystal axes, because some inclusions are invisible from one
direction but not from another. You may also wish to use a pen light at this time.
Magnification is recommended during the examination. In the field a head loupe
is most practical.
Once you are qualified and you desire to buy rough, here are some guidelines
for evaluation. Analysis of rough gemstones might be separated into two general
categories. The first category is perfectly cleaned, cobbed (hammered) rough.
Found in this category are generally gemstones of lower priced species.
This saveson relatively expensive labor by cobbing perfectly clean stones. Because
of the homogenous nature of this type of rough gemstone material, it is possible to
use some formulas to approximate gemstone recovery. Even here there may be some
variation due to things such as cleavage, preforming and cutting techniques,
SECTION III/ CUTTING (MANUFACTURING)
The species we usually apply these formulas to are the more commonly found,
less expensive ones. On particularly clean lots of other material, we may
sometimes apply these formulas: 1) All stones cut to the closest standard shape
and the nearest calibrated size = 20% recovery. Often we call this one for one,
meaning one carat for one gram; 2) All stones cut to the closest standard shape
with no consideration given to calibration = 25% recovery; 3) All stones cut to
the nearest shape and size, including free forms (in other words, cut to proper
height proportions and angles but with no consideration to girdle shape other than
recovery) = 28-30%.
The second category is mostly for more expensive grades of rough. Here, the
time and expense of using a more skilled and costly sawer/former to shape the
stones make it more practical. Greater skill can translate to greater weight
recovery and to more beautiful stones.
This second category ("closest shape, uncalibrated") is not only the largest by
far in amount of money but is also the largest in weight. The reasons that most
rough material is not cobbed perfectly clean are: 1) The time and effort to
carefully examine and work these pieces is more than compensated for by the
extra profit produced by the larger and/or more valuable gem(s) recovered by this
effort; 2) Most miners are not equipped to cob properly; 3) Many mine owners
feel that, through their negotiating techniques, they will get a better price on more
complex mine-run rough; 4) Not all processors of rough will work the material in
the same manner (i.e., some part in different shapes, cabochons, beads, carvings,
etc.); 5) The mine owner's formers cannot project different markets of different
buyers as the processor's formers can.
Then how is this miracle of calculation achieved many times, day after day, in
trading centers throughout the world? First, the mixed lot is broken into smaller,
relatively homogenous, lots that are to be processed the same way. Then we
evaluate a sample group from each lot, and the percentage of recovery of this
sample is multiplied by the total weight of this group. The result is the
approximate recoverable weight for the lot that is then multiplied by the price per
gram that the appraiser gives. Finally, the money value of each lot is totaled and
thus an evaluation is reached.
To calculate by the second method requires the mind's eye to jump into the
rough and to position the possible gems that could be cut. Then look into the
hypothetical tables of those cut stones to see the hues, tones, inclusions,
crystallization and sizes of those stones to evaluate them. Someone who is not
experienced in the cutting and sawing of the material should not do such mental
gymnastics (trigonometry). I repeat this because it is most important.
ANYONE WHO IS NOT EXPERIENCED IN THE SAWING AND FORMING OF
SUCH ROUGH SHOULD NOT DO EVALUATION OF ROUGH GEMSTONES!
Once you've evaluated the rough, you have to negotiate for it. Precious gem
mining is a one-time harvest. Miners rarely look for a continuing relationship. If
they can't get you when they have you, they may not get another chance. Many
times the offers they make are astronomical in relation to the value. Many times
they don't even have a clear idea how much the goods are worth. They are always
afraid of being taken advantage of. And they often are.Miners are interested in
selling the whole production at one time. Picking a lot often makes the negotiations
more difficult. A somewhat easier technique is to offer to buy the lot as long as you
can refuse a percentage. Negotiate the percentage and thereby you are indirectly
As a guide to what price you should offer, insist that the owner of the
merchandise make the first offer. Calculate how much above the value of the
goods the offer is and make an equivalently low offer. For example, if the miner
(or more often the broker), offers the goods for one thousand and you estimate the
value at one hundred, offer ten. In this way you are negotiating in the same form
and usually will gain the respect of the other side.
Subject: Re: sapphires polishing
Date: Sat, 15 Nov 2003 17:44:13 +0800
From: Stewart Cole <firstname.lastname@example.org>
In one of the last few Australian Faceters September-October
"Facet Talk 133 page 22- 24. Is a summary of a talk by Eric Oliver
on getting the best out of sapphire rough.
Since its an Au meeting will be mainly concerned I guess with Au
sapphires. However its a very good summary of the answer to your
Sorry I cant find the article online but email
David Pike email@example.com He may have an electronic copy.
Subject: Re: Followup on sander
Date: Sun, 16 Nov 2003 00:44:06 EST
Jimmy: You gave me the exact answer I needed. There was a set screw on the
rear of the sander plate. Access is through a drain hole in the bottom of the
splash pan. To prevent having to remove the pan each time I'll drill a new hole
in the top and voila' I can mount any thing I want. Thanks for the help and
thanks to the net. Don
Date: Sat, 15 Nov 2003 14:14:15 +0200
To: "LapidaryArtsDigest" <firstname.lastname@example.org>
From: "birdamlasu" <email@example.com>
Dear Teresa and the other friends,
I am so sorry to hear and see on TV about the fire going on in your area.
I know how hard it is for you. We had recently had fires in one of the
most beatiful islands in Marmara sea. I wish these disasters would not
happen but unfortunately it happens.
How are you all who are living in this area?
Kind regards from Turkey,
Subject: Big sapphires!
Date: Mon, 17 Nov 2003 22:27:23 +0000
From: Andy Parker <firstname.lastname@example.org>
Any body fancy a piece of (admittedly synthetic) sapphire rough a foot
across ! came upon this while surfing:-
Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
Tel: 01229 584023
Hi Andy, The Dare Devil Faceters might tackle such a piece.
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PERSONALS: (General Lapidary and Faceting)
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Post something from your experiences in gemcutting today!
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Subject: opening a beer
Date: Sat, 15 Nov 2003 22:03:42 -0600
From: Downey <email@example.com>
TIDBITS AND REFLECTIONS~
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but around in awareness.
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