Program Review: At
our February meeting we were treated
to a presentation on faceting by our own Tom Pankratz. Tom has been a member for
quite some time; he has been faceting gemstones for almost three years.With a laptop
and a projector, Tom walked us through steps in the planning of a faceted stone, from
rough to finished polish. He incorporated GemCad
software to show us how he does it at his home lab.
Members asked questions about the amazing predictions of the software to guide us
toward grinding the correct angles of the facets. Tom's example was the round
brilliant cut, a popular cut for many different gemstones, especially diamond. As
most of us do not have access to rough diamonds, he tweaked the plan for stones such as
quartz and ruby.
He offered us tips on grits to use and the importance of accuracy in each facet's setup
to ensure a better cut. Tom explained that "cut" is one of the features
that jewelry and gem appraisers use in determining the value of a gemstone.
Tom has faceted everything from fluorite (soft) to beryls (hard), as relative to each
other on the Moh's Scale of Hardness.
One of his goals in the hobby is to facet at least one of every major gemstone
known. His approach to choosing cutting material is to salvage the beauty of broken
rough, and not taking a good crystal specimen and sacrificing it into another form.
Tom, an avid mineral collector, flintknapper, and faceter, appreciates nature's
"faceting" process, as well.
He taught us features of certain major gemstones to look out for to arrive at the best
end-product, such as ruby's dichroic (or two-color nature). It is important to
orient your start point to derive the maximum color, as one goal to showing off it's
inherent purple and two-reds.
He cautioned us on working such materials as Kunzite (a lithium aluminum spodumene),
and orienting your facets 15% relative to your starting point, as key to success. A
beautiful kunzite is a terrible thing to waste.
We visited the round cut faceting scheme, which consists of table, cullet, girdle,
pavillion, and crown facets. Tom says that he visits each facet three times, during
his working the stone from cutting to final polishing. Each must be "perfect in
relation to each other, or you can see it from a mile away."
Tom also suggests that "sight is the best tool for judging your work."
There are measuring instruments, computer programs, and the like, but the light play
exhibited by the stone is the major testimony to a job well done.
By maximizing the refracted light, Tom tells us, we can best see the beauty of the
stone. By "tracing the rays" through our project stone, calculated in the GemCad software package, we can see how much light is
purported to be exiting the stone, and not reflecting back to our eye. He showed us
with a real-world example, by employing a green laser pointer and his largest, 400-carat
faceted quartz. By picking up the quartz by its girdle, and pointing the laser light
through the table or crown facets, we can witness the bouncing light rays, thus
demonstrating his point.
Tom covered some buying techniques for gemstones to help guide us to a better purchase.
The general principles, known as the "Four Cs", are "Color",
"Cut", "Clarity", and "Carat Weight", are the basis for a
good decision. Tom added, "Composition" (material from which it is made,
etc.) and "Country of Origin".
An example of Tom's additions are "man-made simulant-vs.-natural" in
composition. The lab-grown material may sell for less than the natural, even though
both have the same composition. A clearer example is "leaded-glass
crystal-vs.-natural garnet". When faceted, both can make deep red bead.
It may be difficult to see the difference, but the man-made glass can cost less.
An example of "Country of Origin" is the comparing of "Tanzanian
rubies-vs.-Burmese rubies". Both red corundums are naturally occurring and held
by many eyes as beautiful. However, the Burmese stones may hold higher prices, due
to a buyer's value of "tradition." Ultimately, it is your choice.
"If you like the stone, buy it," Tom suggests.
Tom also discussed with us optical characteristics of a finished stone, such as
"windowing" and "extinction". There is much more to learn here.
And, many members were intrigued to find out more. There are books, websites,
software, tools, and other resources available to us. The best, though, is a live
demonstration.
It seems complicated, but all of these techniques comprise much knowledge and wisdom
gained by Tom from his learning process. He is willing to share these, and more,
with us at his live faceting demonstration at our March 4-5, 2006 Show. See you
there.
Thanks, Tom.
[Ken Casey]
Links
GemCad Software
Gemological Institute of America
American Gem Society
Columbia-Willamette Faceters'
Guild
United States Faceters Guild
Midwest Faceters Guild
Gram Faceting
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(Left): Tom proudly shows us the largest stone he has ever faceted.
(Above): Left, a man-made ruby boule. Right, opaque corundum