Russian Alexandrite
In April of 1834, alexandrite was discovered in the emerald mines close to the Tokovaya River in the Ural mountain region of Russia. These first alexandrites, according to the Gemological Society of America (GIA), were said to be of fine quality, and had remarkable color change properties as well as vivid color. Alexandrite was named after the Russian Czar Alexander II, and it became the country's national stone because its colors were like that of the Imperial Russian flag.
Composition
Alexandrite is from the chrysoberyl family that has three major types. One type, according to the International Colored Gemstone Association (ICA), is the colorless or transparent yellow chrysoberyl. The next type of chrysoberyl is cat's eye, and the last type is the color-changing alexandrite. What makes alexandrite different from the rest of its family, though, it is has iron, titanium and chromium, which is classified as a major impurity. It is the chromium, however, that gives alexandrite its distinctive color-changing properties. Alexandrite is a hard stone, rating on the Mohs scale of hardness at 8.5. A diamond is a 10 on the scale.
Color
The most sought after alexandrites, according to GIA, are green in daylight and change to red or a slightly purple-red in lamp light or candlelight. In some alexandrites, the red is a raspberry red. One thing to remember about alexandrites, though, it is the alexandrite's ability to change colors that has made it one of the most valuable gemstones in the world.
Clarity
Russian alexandrites are often transparent, according to GIA, and typically have good clarity, but they can contain fingerprint or silk inclusions. Inclusions are flaws in a gemstone that can take the form of a gas bubble, crystal or pocket of liquid, according to Gem Select. An alexandrite up to one carat in size, without any visible inclusions is rare, and alexandrites larger one carat without inclusions is extremely rare, according to Khazagems.
Availability/Cost
Russian alexandrite, according to the Alexandrite Tsarstone Collectors Guide, was extensively mined between the years of 1840 and 1900, and the supply of Russian alexandrite is thought to have been depleted by 1915. Due to the rarity of alexandrites, they are costly. In 2007 to 2008, alexandrites sold between $100 and $15,000, depending on color and quality. Russian alexandrite can be more valuable than these amounts if it is of superior quality and can be verified as Russian alexandrite.