Could you tell me what year they started making synthetic
Alexandrite I have a client who has a ring from the sixties and
asked me this question
The year was 1973, but that doesn't necessarily mean your client's
stone is natural, or even alexandrite. Color-change corundum was
developed around 1909, and has been purchased by unsuspecting people
ever since, as alexandrite for birthstones. It is still widely
offered as an affordable birthstone alternative to natural
alexandrite. Check your supplier's catalog. If they practice full
disclosure, you'll see what I mean...read the fine print. Most of us
have Rio Grande's Gems and Findings catalog. Check their simulated
(not synthetic) alexandrite listings.
Actual synthetic alexandrite has been maufactured by both the
Czochralski and flux methods, and the most obvious difference is in
the inclusions. Flux veils, gas bubbles, metallic platelets and
curved striae will be evident in synthetic alexandrite, depending on
the method of manufacture. Also, synthetic alexandrite often has a
stronger reaction to UV light than natural does. Additionally, both
synthetic types have modifying hues in their color changes that
differ from each other, and from natural material. Natural
alexandrite from different locations also vary in color.
Synthetic color change corundum can have similar inclusions to
synthetic alexandrite owing to similar manufaturing processes.
Refractive index and birefringence are also different. Specific
gravity is another clue, but you'd have to remove the stone to check
To sum up, the year your client's ring was made is a very weak
indication of whether it contains a natural alexandrite, but it is a
start. Any experienced gemologist can tell, and most of us do IDs
for reasonable prices, i.e., the cost of a decent lunch or dinner. If
it is a natural stone, a written appraisal would be worth the extra
James S. Duncan, G.G.
James in SoFL