Jamming Gems Alexandrite Info

Alexandrite

General Information:
The rare and unique gemstone Alexandrite is the gemstone for the month of June. Alexandrite was discovered in 1831 in Russia, on the first day that the Russian czar Alexander II came of age. For this, the founder named the gemstone after the czar. Alexandrite is a very rare mineral that comes from a variety of chrysoberyl (BeAl2O4). Chrysoberyl occurs in granitic pegmitites and mica schists. Alexandrite is known for its unique characteristics to change color from green to red. This color change is created when, amounts of alumina replaces chromic oxide. To see the color change in an alexandrite, look at the stone under incandescent lighting, and daylight.
Alexandrite with more color change is considerably more valuable, some gems will change 100% and others as little as 5% of a change can be seen. The most desired colors of alexandrites are the pure red and green, but they sometimes have a brown or blue hue to them.

Origin:
Russia has long been the most known and desirable source for Alexandrite. It has also been found in Brazil, but these alexandrite mines are currently under control by the government. Alexandrite found in Sri Lanka usually has very low color change, often times being able to be seen under laboratory conditions only.

Common Treatments and Lab Created Forms:
There is no treatment done on alexandrite.
There are several alternatives to the expensive natural alexandrite gemstone. Lab created chrysoberyl has been created and is on the market for significantly less than the natural gem. This lab chrysoberyl has the same properties and is identical in composition to the natural alexandrite. All other options for this gemstone are simulants and are not a true alexandrite even though they may have similar physical properties. Lab corundum alexandrite is a popular option, which is lab created sapphire that has a color change similar to that of natural alexandrite. There are also cubic zirconias that change color, and colored glass available.

Physical Properties:
Moh's Scale Hardness: 8.5
Specific Gravity: 3.68 - 3.75
Refractive Index: 1.745 - 1.759
Fracture: conchoidal, brittle
Crystal Habit: prismatic crystals are elongated on c, and often tabular on {001}, with striations parallel to [100]
Colors: green in daylight and red-violet in incandescent light.