Sorry about this long post, folks, but I think it’s useful to anyone
following this thread who is considering studying with GIA for their
One very major consideration of taking the GIA Distance Education
courses is the very expensive need of certain gemological testing
equipment for the final course, Gem Identification. Of course, it
will be months before you’ll need the equipment, since there are four
prerequisite courses before Gem ID. Several of my Extension
classmates took as long as five years to complete the entire program.
Required equipment includes a 10X triplet loupe. Triplet means that
it 1) magnifies, 2) is color corrected and, 3) is corrected for
spherical abberation (distortion). Decent triplet loupes can be had
for under $20US. Although a loupe is handy, trust me here, you will
want a gemological microscope with darkfield lighting. Get the best
one you can afford. A zoom model is best, but I got by just fine with
an inexpensive 10X/30X relatively inexpensive model (Gem-Oro). The
darkfield well makes a big difference.
You will also be required to have a gemological refractometer to
measure refractive index of gem materials (there are refractometers
for other purposes). GIA’s model is very expensive at $659US, but
others have told me there are cheaper ones available on eBay.
However, I’ve been told that while they are fine for taking readings
on flat facets, they don’t work well for spot readings on cabochons.
I’ve never used one other than a GIA model, so I can’t say for sure.
This is the one piece of equipment you will use to test every gem
material (yes, there are faceted stones, cabochons, beads and even
The next requirement is a polariscope to check for double
refraction, interference figures and several other tests. GIA’s costs
$339, but anyone handy with a few tools can make one out of a length
of PVC tubing, a saw, two polarizing filters available from Edmund
Scientific and a light bulb. If you make your own, I strongly suggest
the glass type of filter, not the plastic kind as they don’t work as
well. You can also get glass polarizing filters from camera supply
stores but the ones I’ve priced aren’t very cost effective when
compared to a manufactured refractometer. I’ve even taken apart a
cheap pair of polarizing sunglasses to use in a pinch. It worked, but
I wouldn’t want to attempt the Gem ID course with it. The GIA model
includes an interference figure sphere that can be very handy with
Gem ID, although most gem materials are loathe to give up the figure
(you’ll learn more about this in the coursework). Before I gave up on
my plastic-lensed polarizers, I had a glass blower make me a couple
spheres of differing sizes to try out. They all worked fine. Any
glass woker can do it, as the glass likes to ball up on the end. It
simply needs to be as spherical as possible with no gas bubbles
inside. So, imagine using a “third hand” with two alligator clips,
clipping two sunglass lenses to it, orienting them, holding a
penlight (or hand torch in th UK) underneath while positioning a
gemstone on it’s interference axis while touching an interference
figure sphere to the stone. It can be done, but you really have to
like gemology to bother with it.
The fourth, and final, requirement is a dichroscope to test for
dichroism. Two types are widely available: plastic “Polaroid” type
and the calcite type. I strongly recommend the calcite model. While
rummaging through my older gemologist friends’ dichroscopes, I’ve
never found an old polaroid one that works, but the calcite ones
always last, as long as they’re taken care of.
So, those are the four main pieces of equipment a person is required
to own or have access to, while studying Gem ID. There are others
that are just as worthwhile to have, and I’ll get to those in a
moment. I want to point out that GIA has a Mentor Program. They
started it just after I finished my program, and I wish it had been
in place before I started. Basically, there are G.G.s in the trade
who have volunteered their time and equipment to Distance Education
students who are in the Gem ID course. There may be a mentor in your
area, or not. If so, (s)he can not only lend equipment, but expertise
as well. They are not allowed to help with your ID, but can be of
immense assistance in learning the ins and outs of using the
Now, on to some other handy things to have…
Spectroscope. Gem materials absorb and reflect light in varying
ways. Spectroscopy is a difficult application, but can be a telling
separation. Spectroscopes display the visible spectrum of light and
will show lines of absorption at different frequencies. Often, they
can make a big difference.
Specific Gravity. Best done with a scale, SG can be a huge boon.
Basically, you weigh an item in air, then weight it in water. Apply
a simple math equation and you’re done. Many gemologists make this
dtermination before many others, but GIA relies more on refractive
index (RI). RI’s overlap, and so do SGs. But rarely do they overlap
to the point where both readings won’t separate natural gemstones.
Hanneman (no, not Hanuman) Gemological Instruments makes a neat SG
balance scale that can be valuable, but it isn’t very portable. I
rigged up my own Frankenstein-like wire thingy to use with a shot
glass to weigh in water. Anyone can do the same. Just have a very
good carat scale. There are also SG liquids that can help a bit.
While not as pinpoint accurate as a scale, they can be very helpful
in separating gem materials. With practice, they can be extremely
A Chelsea filter can be useful in separating some as can
the variety of filters available from Hanneman. In fact, Hanneman
has lots of gadgets and geegaws for inexpensive gem testing, too
numerous to mention here. I don’t have the address or contact info
handy, but can post it later if requested. If you order the catalog,
don’t be unimpressed with its spartan look. Last one I got was a
couple of photocopied pieces of paper. It’s all real-deal stuff, but
some of it IMHO is best used by the more experienced gemologist.
Longwave/Shortwave utraviolet light with box. While not absolutely
necessary, this can absolutely prove your separation at the end.
Certain gem materials act differently under UV light, and shortwave
can be just as telling as longwave. It is worth having.
There is plenty of other equipment that can come in handy, but these
are the ones I use most often in descending order.
Now, with apologies to Carrie Nunes and several others who have
asked me if I know of any used equipment over the years, I have
recently stumbled upon some. While rummaging through my employer’s
old equipment, I have found a few things of interest. A calcite
dichroscope, diffraction grating spectroscope (metal body, sliding
focus type), polariscope and chelsea filter - all GIA and all in
workling order. There is also a GIA refractometer with a fairly
scratched hemicylinder that I am going to try to lap clear on my
faceting machine soon. If successful, the boss has authorized me to
offer this “Gem ID Kit” for $620. His first thought was eBay, but I’d
rather offer it to this group that has helped me so much. I’ll let
everyone know how it works out. If it doesn’t, the rest of the
equipment will be available for a very reasonable price.
James S. Duncan, G.G.
James in SoFL