I'm no gemologist but to say for sure yes or no you need a
couple of tests.
Actually, to tell the synthetic corundum (sapphire) from genuine
alexandrite can be done by eye, as the colors are not the same.
the synthetic changes color, yes, but from a steely
blue/grey/green yucky sort of thing to an amethyst-like purplish
color. alexandrite, the real ones, don’t look like that…
The testing you need, though, is a simple refractive index
measurement, if you wish to be sure. This doen’st tell you
real/vs synthetic, but it tells you corundum vs. Chrysoberyl in a
GIA may charge a hefty sum, but I seriously doubt that most
gemologists would charge that much. As I said, with a bit of
experience and training, most of us would be fairly comfortable
doing that determination by eye alone.
Everytime I tell one of these owners the truth about these
stones they get mad as hell! Now I just look at them and say
"Sure looks real to me"
I’d suggest to you, Preston, that you’re not doing them any
favors by hiding the truth here. Especially if you then wirewrap
a nice piece of jewelry for a price… There are ways to let
people down gently with these stones. At the same time as you
let them know it’s not a genuine alexandrite, let them know these
stones have been made for quite a long time and are interesting
in their own right. Besides, though not alexandrite itself, they
ARE the stone that’s widely used in it’s place, in class rings,
mothers rings, etc. So they are not completely unacceptable.
Also, point out that whatever they are, they are pretty, and
quite hard and durable.
Also, though I don’t know whether some family in Mexico makes
these, I do know that if that’s the case, it’s only a very minor
source of the stuff. It’s made by a number of manufacturers in
europe, the far east, and the U.S., along with the other colors
of synthetic corrundum and spinel.