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Alexandrite

Alexandrite is a mineral (BeAl₂O₄) with a Mohs hardness of 8.5 and a vitreous luster, usually green, red or purple.

The color-change variety of chrysoberyl: green in daylight and red or purple under an incandescent bulb.

Alexandrite specimen
Photo: Parent Géry, Public domain, via Wikimedia Commons

How to identify alexandrite

  • The same stone looks green by a window and reddish under a warm lamp.
  • Hardness 8.5 — harder than topaz.
  • Ural stones change the most; many newer ones only shift from teal to purple-brown.

Often confused with

Where it's found

  • Ural Mountains, Russia
  • Hematita, Minas Gerais, Brazil
  • Tanzania
  • Sri Lanka
  • India

Uses

Gemstones.

Rock tumbling

Not suitable for tumbling. Gem rough this valuable is cut, not tumbled.

Did you know?

Chromium in the crystal absorbs the middle of the spectrum, so daylight (rich in blue-green) and a warm bulb (rich in red) show different colors.

Alexandrite FAQ

What is alexandrite?

Alexandrite is a mineral (BeAl₂O₄) with a Mohs hardness of 8.5 and a vitreous luster, usually green, red or purple. The color-change variety of chrysoberyl: green in daylight and red or purple under an incandescent bulb.

How do you identify alexandrite?

The same stone looks green by a window and reddish under a warm lamp. Hardness 8.5 — harder than topaz. Ural stones change the most; many newer ones only shift from teal to purple-brown.

How hard is alexandrite?

Alexandrite has a Mohs hardness of 8.5. Alexandrite scratches glass, and a steel knife can't scratch it.

Where is alexandrite found?

Notable localities include Ural Mountains, Russia; Hematita, Minas Gerais, Brazil; Tanzania; Sri Lanka; and India.

What is alexandrite used for?

Gemstones.

Can you tumble alexandrite?

It isn't a good choice for a rock tumbler. Gem rough this valuable is cut, not tumbled.

What is alexandrite often confused with?

Alexandrite is most often confused with Chrysoberyl, Emerald and Ruby. Ordinary chrysoberyl stays yellow-green in every light. Emerald is softer and does not swap green for red. Ruby stays red and is harder still.

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