I have a couple degrees in geology and mineralogy…whoopee.
I think I learned more about minerals and crystals in one semester
of mineralogy than a GG learns in the whole course. I don’t recall
anything in GIA’s literature that discusses tektosilicates or Miller
indices, for example, and a basic understanding of such things really
is necessary before much useful learning can take place concerning
our little gemstone friends.
I don’t mean to slam anyone, but GIA’s intention with the GG courses
is to train jewelers and others who do not have a scientific
background, as much as can be done, given that shortcoming. It should
be considered an introduction to mineralogy, at best. I know of
nothing in GIA’s courses that would lead anyone to think freezing an
emerald might be a reasonable part of the “oiling” process.
I’ve been cutting stones for almost four decades, and the idea of
freezing an emerald, especially a client’s emerald, makes me cringe.
The very last thing you EVER want to do with a crystal that may
contain fissures, dislocations and two or three phase inclusions is
to heat it or freeze it. Little is accomplished by freezing except to
risk loss of the stone.
There are many ways to simply “oil” an emerald, from using a simple
penetrating oil like WD-40 (works great, by the way) at a 10 hour
room temperature soak, to using a vacuum chamber to help capillary
action pull a more viscous oil into the emerald while air is
evacuated from the fissures.
All oiling is transient, but some is more persistent than others,
and most oils will accept a vegetable or aniline dye.
If one is interested in a more permanent and difficult-to-detect
solution, there are a couple of proprietary methods available. Usual
cost is around $100/c, your risk. Very, very durable. There’s
usually an ad for this in Colored Stone magazine, I think.
There is a ton of available in the literature. Gems &
Gemology did a very good article on this subject a few years ago,
I’m sure back issues are available. Any number of books discuss the
process in depth for the person who is not too lazy to search them
out. John Sinkankas’s “Emerald and Other Beryls” is a great place to
start, as well. That work is a little dated, technologically
speaking, but simple oiling is pretty low tech.
All treatments require disclosure, of course.