I’ve never encountered a stone called “Alexandra,” but know a fair
amount about one called “alexandrite” since I deal in it. I suspect
your search for will improve if you use that spelling.
Alexandrite is a rare and expensive color-change variety of the
mineral chrysoberyl, exhibiting various shades of red/purple in
incandescent light and green to blue-green in daylight and
fluorescent light. Chrysoberyl also occurs in green to yellow
crystals without color change, and they make fine faceted stones of
excellent hardness (mohs 8.5). When “silk” fibers are present they
cause an effect called “chatoyancy”: the cat’s-eye phenomenon.
Chrysoberyl (or cymophane) cat’s-eyes are the finest available and
are very expensive in large sizes and fine color. They are the only
stones that can accurately be called “cat’s-eyes” without a modifer
such as “cat’s-eye tigereye,” “cat’s-eye tourmaline,” etc. One of
the rarest stones on earth is the alexandrite cat’s-eye: a
chrysoberyl cat’s-eye with color-change! Ironically, it requires a
modifier to distinguish it from “cat’s-eye.”
Alexandrite is in a class by itself. It may be the world’s most
expensive stone (in top quality and large size) but very attractive
smaller stones with less than ideal color change are available more
reasonably. Beware the large amount of man-made "alexandrite"
currently on the market. Lab-grown stones are abundant, and some of
the sellers I’ve observed aren’t entirely forthcoming about their
stones’ origins. This is a case where a few natural inclusions can
be a mighty good thing!
Alex was not discovered until 1830 in Russia’s Ural Mountains.
Because its colors were the same as the red and green of Czar
Alexander II’s Imperial Guard, it was named after him. Some stories
claim it was discovered on his birthday but I suspect that’s
stretching the truth a bit. It makes a charming tale though.
Russian Alexandrite was always scarce and became even more so after
the 1917 Bolshevik Revolution. Tiffany and Co. played an important
role in popularizing alexandrite in the U.S. as the company has done
with a number of stones, most recently tanzanite and tsavorite.
The alexandrite supply dried up almost entirely for many years, with
only a few stones of variable quality from Sri Lanka until another
deposit was discovered in Brazil in the late 1980s. Despite what
I’ve read here and elsewhere, the Brazilian gems can be as good or
better than anything ever produced in Russia. I’ve compared them
side-by-side with my own eyes. The Brazilian mine is now largely
exhausted but a few stones are still trickling out, and I can
occasionally find them mostly in smaller sizes. Some high quality
large alex’s are also being found in Tanzania and Madagascar but
production is spotty and sporadic.
I am involved with a brand new alexandrite source in Asia, and
receive occasional shipments of small faceted stones as well as small
cat’s-eye alex’s. Occasional center stones are available in various
qualities. However, if you’re looking for a 2-3 carat clean gem of
fine make with 100% top color change and haven’t done any price
shopping, fasten your seat belt and take a few dramamine. You’ll
need them when you hear the price; but if you’re serious I may be
able to find a suitable stone. If you’re simply seeking a birthstone
for June you’d be better advised to settle for something under 1
carat with inclusions and a 50 to 75% color change. They are still a
remarkable work of nature!