Alexandrite
Varietyof Chrysoberyl
Alexandrite is the color-change variety of chrysoberyl, green in daylight and red under incandescent light. As a variety of Chrysoberyl, it shares that species' composition (BeAl2O4), crystal structure, and hardness; the distinction is the appearance defined above.
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About Chrysoberyl
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Chrysoberyl species page.
| Formula | BeAl2O4 |
|---|---|
| Hardness (Mohs) | 8.5 |
| Specific gravity | 3.5-3.84 |
| Density (calculated) | 3.709 |
| Crystal system | orthorhombic |
| Color range | brown, green, red, white, yellow |
| Luster | vitreous |
| Streak | red |