Alexandrite

Alexandrite is the rare color-change variety of chrysoberyl, a beryllium aluminum oxide. Trace chromium causes it to absorb light in a way that makes it appear green or bluish-green in daylight and red or purplish-red under warm incandescent light, the phenomenon known as the alexandrite effect.

First found in Russia's Ural Mountains in the 1830s and reputedly named for the future Tsar Alexander II, it became a symbol of imperial Russia, whose colors were red and green.

With a Mohs hardness of 8.5, alexandrite is both durable and exceptionally scarce, making fine specimens among the most valuable colored gems.

Alexandrite forms where beryllium-rich and chromium-rich geochemical environments meet, an unusual combination since these elements rarely occur together. It typically develops in mica schists, pegmatites, and metamorphosed contact zones where beryllium-bearing fluids interact with chromium-bearing host rocks.

The original deposits were in the emerald-bearing mica schists of the Ural Mountains, Russia. Today significant sources include Brazil (notably Hematita), Sri Lanka, and East Africa (Tanzania and Madagascar), though strong color-change material remains rare from all localities.

The defining test is the color change: examine the stone under daylight or fluorescent light (green/bluish-green), then under incandescent or candlelight (red/purplish-red). A strong, distinct shift is diagnostic and hard to fake convincingly.

Alexandrite is hard (8.5), has a vitreous luster, white streak, and high specific gravity (~3.7). It is often pleochroic. Look-alikes include color-change garnet (different color shift, lower hardness), color-change sapphire, and synthetic corundum or spinel sold as alexandrite imitations. Lab testing confirms the chrysoberyl identity and natural origin.

Alexandrite is used as a premium faceted gemstone in rings, pendants, and earrings, valued chiefly for its color-change and rarity rather than mere color. It is a June birthstone and the 55th-anniversary gem.

Fine natural stones with strong color change and good size are extremely expensive, often rivaling or exceeding top sapphire and ruby per carat. Cat's-eye alexandrite, showing both chatoyancy and color change, is especially prized. Much affordable "alexandrite" in jewelry is actually lab-grown corundum or true synthetic alexandrite. Metaphysically it is associated with balance, intuition, and renewal.