Regarding gemology courses, education is always helpful. The GIA
course or the FGA cert (UK) or Canadian Gemology Assn. course are all
great for learning and giving you a recognized certificate. However,
if all you are after is gemology knowledge and you don’t have a need
for a certificate, there are a number of on line schools and even
some free on line courses (such as Barbara Smigel’s very nice
offering). You can also teach yourself gemology either on line or
through books. As I stated in another thread, if you can read through
and thoroughly understand Hanneman’s book, Affordable Gemology,
you will know more than most GIA graduates and be able to ID and
separate gems without expensive instruments, which look nice in your
office or store, but aren’t necessary from most ID.
I say this as someone who completed the GIA gemology course in 1996
and also did a lot of self-study. While I learned some things from
the GIA course, my study of books before and after that actually
taught me just as much. As I mentioned in the recent earlier thread,
Antoinette Matlins’ book, Gem ID Made Easy, is a great starting
As to glass, yes, window glass doesn’t have bubbles, but who makes
gem imitations out of it.
And glass does have a concoidal fracture, but so does quartz. If you
use enough magnification, most natural gem materials have inclusions.
Yes, glass often has telltale bubbles or swirls.
Also if it’s old, it will have a lot more wear than quartz and is
warmer to the tongue than crystalline materials. In a faceted stone,
the rainbows seen when the stone is held up to the eye will
differentiate quartz from glass. Glass will show one single rainbow
with the colors in a typical row (ROYGBIV). Quartz, being
birefringent, shows two overlapping rainbows, which look a little
different. This is part of the Hanneman-Hodgkinson method of gem ID
Good luck with gemology, it’s fun!