We are looking for some about the synthetic
precious gems.A french company talk us about the Verneuil
method in order to produce synthetic gems, but we don’t know
exactly this method.Thank you in advance.
There are many type of synthetic stone. The most common precious
varieties are corundum (including ruby and sapphire),
produceable in every color, and synthetic emerald. For each of
these gems, there are several processes used to produce them.
I pulled this from “Ruby and Sapphire”, by Richard
W. Hughes, the most complete book available on the subject. If
you want to really learn about them, you should have this book.
I’m quite sure I can arrange for one to be sent to you if you
can’t find a copy where you are. Cost is a little over a
hundred dollars, but it’s worth it.
The Verneuili process was discovered and perfected by Auguste
Verneuil (1856-1913) a French chemist. The method is to this
day relatively unchanged, and accounts for 90% of the world’s
synthetic corundum production. In essence, aluminum oxide
powder is sifted through a hydrogen flame, and heated to 2,200
C. This deposits on a molten ‘glob’, or boule, located below
the flame, and grows upward. Because of this process, the
trademark way to spot a Verneuili ruby is to look for curved
growth lines in the stone itself, sort of like the 'fingerprint’
on the underside of wax that has dripped from a candle. Natural
corundum never displays curve growth lines. Gas bubbles are
sometimes present, also an indication of Verneuili stones. Kurt
Nassau is the most published author in the world on the subject
of synthetic gems. I should know more about them, because my
grandfather was greatly involved in this and was Mr. Nassau’s
boss at Bell Laboratories in New Jersey, where I was born. I
have many boules of synthetic corundum and spinel that they made
in the 60s and 70s. I’ve even cut some of them here. A little
historical connection… Hope this helps you a bit.