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Color Stones


#1
   I am curious whether there is any machine/hand device/instrument
which could identify color stones... checking pearls... diamonds,..
what best devices would Orchidians suggest? 

Lalit, While there are a few types of “meters”, notably reflectance
meters, that purport to identify stones easily, they are limited, and
not always all that accurate. You really need, for this type of work,
several instruments, and either the formal gemological training, or
self study from books, to use the correctly.

First and formost, you need a good gemological microscope. More than
any other single instrument, this will tell you a great deal about
most stones, as well as pearls, diamonds, and even be useful in
determining the overall quality of jewelry work too. It needs to be a
darkfield binocular microscope, and for colored stone identification,
magnification higher than 10x is usually needed. 30x will do it, but
higher is better for some of this. The microscope is your primary
tool to detect substitutes and synthetics, by analizing the
inclusions and defects in a stone.

For basic gem identification, you then usually must have both a
refractometer and a polariscope, at a minimum.

With these three items, you can do most identifications, especially
with loose/unset stones. Sometimes, with set stones, or unusual
items, you will need more specialized equipment, like a good
spectroscope. This is a highly useful tool in many cases, but is
often considered a secondary instrument after the first three. Still,
there are some cases where nothing else will tell you what you need.

And a good basic set of specific gravity liquids can also be very
useful with loose stones. they are fairly inexpensive, so it’s silly
not to have them.

another inexpensive item that sometimes is a very quick way to tell
certain stones is a simple dichroscope.

You’ll need a good ultraviolet lamp too. It’s best if you’ve got one
that gives the option of short wave UV, in addition to the long wave
thats most commonly needed.

Those are the basics in instrumentation. But the real key is
knowledge. I’d suggest that you enroll in the professional
gemological training programs offered by several gemological
organizations around the world, including Britain’s Gemmological
Society, or the GIA in the US, both of which offer training by
corrospondence or in locations outside of their home bases. GIA, for
example has a campus in asia as well as in the US, where they offer
classes all around the country. If you cannot afford formal training,
at least buy several good books on gem identification, and study them
carefully. If you’re well enough trained in what to look for in a
gem, and how to look, you can do perhaps 90 percent of the
identifications you’ll need with just a good 10x loupe. You’re
accuracy may not be perfect like this, but it will often be close.
Then for those few stones where you’re not sure, you ask a trained
gemologist for a bit of help…

Hope this helps.

Peter Rowe