Alexandrite

Alexandrite was discovered in 1830 in the Ural Mountains of Russia — traditionally on the birthday of the future Tsar Alexander II, after whom the stone was named. The two colors it displays — green and red — were the imperial colors of Russia, giving it symbolic significance.

Per GIA, alexandrite is a variety of chrysoberyl (BeAl₂O₄) that gets its unique color change property from chromium: in daylight it absorbs red and emits green; under incandescent light it does the reverse. The same chromium that colors rubies red here in a different mineral environment causes green.

Today alexandrite is mined in Brazil (Hematita — discovered 1987), Sri Lanka, Zimbabwe, and Tanzania. The Ural mines are now practically exhausted; authentic Ural specimens are rare museum and auction objects.

Color change optics: Alexandrite absorbs light in the middle-green part of the spectrum and transmits both red and green. Daylight (rich in green) gives the stone a green color; incandescent light (rich in red) gives red-violet. The intensity of color change (the "color change factor") is a key quality parameter: weak, moderate, strong, exceptional. The finest Ural specimens have complete change (100%) — from intense green to intense red.

Ural alexandrite: The Tokovaya mine in the Russian Urals was the only reliable source until the mid-20th century. Ural specimens have legendary quality — intense emerald green in daylight, intense purplish-red under incandescent light. They rank among the world's most expensive colored gemstones; specimens above 3 ct are exceptionally rare.

Modern alexandrite: After Ural mine depletion, Brazil, Sri Lanka, and Tanzania became primary sources. Brazilian stones are often larger but with less dramatic color change. Sri Lankan ones are sometimes colorless-grayish-green with reddish change.

Synthetic alexandrite: Synthetic alexandrites have been available since the 1960s. Chatham and Kyocera produce high-quality synthetics chemically identical to natural. GIA certificates distinguish natural from synthetic. Many "simulants" exist on the market — e.g., color-changing glass or synthetic corundum that is NOT alexandrite.

Price: Top-quality natural Ural alexandrite (above 3 ct, exceptional change) is among the world's most expensive gemstones — surpassing diamonds and rubies of the same carat weight.

Per GIA, alexandrite is one of the rarest and most valuable phenomenal gemstones in the world. High-quality specimens with intense color change (green in daylight → red under incandescent) and weight above 1 ct are exceptionally rare and command prices comparable to rubies and sapphires of comparable quality.

Original Ural alexandrites with clear documented origin are an absolute premium. Most of the modern supply comes from Brazil (Hematita and Alexandria), Sri Lanka, and Zimbabwe — but Ural quality with color change intensity is rarely matched.

Synthetic alexandrite (Chatham, Kyocera) is common on the market and visually convincing — a GIA certificate is mandatory for buyers to distinguish natural from synthetic.

"Emerald by day, ruby by night" — this is how alexandrite was described in imperial Russia. This metaphor precisely captures the dramatic color change from green in sunlight to red under incandescent light.

Alexandrite is one of three gemstones that display both color change and chatoyancy (cat's eye) simultaneously — this occurs when naturally oriented rutile inclusions form a silky sheen parallel to the axis, while the stone simultaneously shows color change from green to red. Such specimens are among the rarest gems in the world.

GIA classifies alexandrite in the same chrysoberyl group as cat's eye (chrysoberyl cat's eye) — both are BeAl₂O₄, the difference being only whether they contain chromium (alexandrite) or parallel inclusions for chatoyancy.

Synthetic alexandrite has been commercially available since the 1960s. GIA CS identifies three production methods:
- Czochralski method (pulling from melt) — produces high-quality specimens
- Floating zone method
- Flux method (solution growth) — GIA: "one of the most convincing synthetic alexandrites is the flux-grown variety from Russia"

Kyocera Corporation (Japan) was the first in 1987 to commercially produce synthetic cat's eye color-change alexandrite — a phenomenal combination that is exceptionally rare in natural alexandrite.

Imitants (NOT synthetic alexandrite, but mimics):
- Synthetic corundum with color change — most common imitation; grayish blue in daylight, violet under incandescent (not green/red like true alexandrite)
- Synthetic spinel with color change
- Glass doublet with a color filter

For buyers: a GIA certificate is mandatory — true natural alexandrite must have laboratory confirmation of origin. Synthetic is sold legally but must be labeled. Color simulants (synthetic corundum) are sometimes sold without disclosure.