Alexandrite

Alexandrite is one of the rarest of all colored gemstones available today. More specifically, it is an extremely rare color change variety of chrysoberyl (a cyclosilicate). Despite its name, chrysoberyl, which is an aluminate of beryllium, does not actually belong to the beryl mineral group, but rather, it is classified as its own independent mineral group.

The history of alexandrite is quite controversial, dating back to the times of Imperial Russia. It is said that the stone was named after the Russian tsar, Alexander II (1818 – 1881), but it was discovered by a Finnish mineralist called Nils Gustaf Nordenskiöld (1792 – 1866). When Nordenskiöld first discovered alexandrite in 1834, it was initially thought to be an emerald because it was discovered in emerald mines located in Russia’s Ural region, near the Tokovaya River. The specimen was later identified as a chromium bearing, color change variety of chrysoberyl. Legends claim that the discovery of alexandrite was made on the very day the future tsar of Russia became of age. Inevitably, the red and green color change stone was to be declared the official gemstone of Imperial Russia’s Tsardom.

The color change phenomenon seen in alexandrite is referred to as the ‘alexandrite effect’. The change in color can be observed under certain lighting conditions, typically under daylight and incandescent lighting. Alexandrite is also a strongly pleochroic gem. It can display emerald green, red, orange and yellow colors depending on which angle the stone is viewed from. The pleochroicproperties of alexandrite are completely independent from its unique color change ability. Typically, alexandrite exhibits an emerald-green color in daylight, and raspberry-red under incandescent lighting. Alexandrite can also occur with yellowish and pink colors, and extremely rare specimens can exhibit chatoyancy (cat’s eye) effects when cut en cabochon. The color change ‘alexandrite effect’ is a result of the strong absorption of light in the yellow and blue portions of the color spectrum.

Alexandrite Color

Alexandrite’s green hue is a result of chromium impurities. Chromium is the same coloring element found in emerald, the green variety of precious beryl. Sri Lanka (Ceylon) alexandrite is known to exhibit a khaki to brown color change. Alexandrite with Zimbabwe origin usually has very little color change and they are typically darker in color with tints of purple. Tanzanian specimens tend to occur with lighter tones and possess moderate to good color change. Brazilian alexandrite is known to be highly saturated and exhibits a blue to purplish color change. The most desirable alexandrites are those with pure hues and a strong color change ability.

Alexandrite Clarity and Luster

Alexandrite stones are typically clean in clarity and once cut and polished, the will exhibit a vitreous luster. Alexandrite in the rough can range from transparent to opaque. Fine alexandrite is considered to be more valuable than blue sapphire, emerald and ruby, especially alexandrite over 1 carat in weight. Sri Lanka is known to produce the cleanest alexandrites, often lacking any visible inclusions at all.

Alexandrite Cut and Shape

Alexandrite is rarely found in large sizes. Any specimens weighing over three carats are considered to be extremely rare. The largest cut alexandrite gemstone weighs 66 carats and is currently located in Washington, D.C.’s Smithsonian Institution. Alexandrites are often faceted in traditional shapes such as oval, round, pear, marquise and cushion cuts, but they are also commonly found in fancy shapes such as heart and trillions cuts too. They are not typically cut en cabochon, unless they possess chatoyant properties.

Alexandrite Jewelry

Most large alexandrite gemstones can only be found in old period jewelry, since new material is so extremely rare. Many English Victorian jewelry designs feature alexandrite stones, but mostly smaller stones. Antique Russian jewelry designs are famous for using some of the largest alexandrites available.

Alexandrites are a hard and durable stone, and so they are ideal for any jewelry design such as rings, earrings, pendants, brooches, pins and pendants. Since they are often very small and expensive, they are usually set and utilized as accent stones rather than center stones. They are perfect for creating halo jewelry designs as well as eternity and anniversary bands.

Source: Gem Select