Hi Barbara and All, I am not sure how big "giant" is from your
description. The fact that the "emerald" stones are clean to the
eye, or have polish marks on the table is not proof they are
synthetic, treated, or imitation.
However, the market contains a large amount of man-made (synthetic)
variety of gems in very nice settings that are not cheap. You still
get the great look at less money. Thus it is possible they were
Gilsons, Chathams, or some Japanese or Russian synthetics. Then
again at $12K they could be natural.
"Mystic Topaz"... I think that is the name being used for the
diffusion treated topaz. The topaz raw material is natural and near
colorless when it comes out of the ground. This material is then
cut, put into a chemical mix, and then heated for a specific
duration. Over time the treatment diffuses into the natural material
creating the color. The distance which the diffusion penetrates into
the cut gem is dependent on the length of time of the treatment.
Normally the treatment is only a few thousandths of an inch deep I
believe. If these stones are recut they generally lose their color
since it is only skin deep.
Hope that helps,
Steve Green - Rough and Ready Gems www.briolettes.com
Gemstone briolettes and precision ultrasonic drilling