Chrysoberyl
Mineral BeAl2O4
Also called Cymophane and Cat's eye
About it
Very hard, yellow-green tabular crystals, often twinned into six-sided wheels or hearts. Varieties are colour-changing alexandrite and silky cat's-eye; found in Brazil, Sri Lanka, and the Urals.
- Type
- Mineral
- Group
- Oxide
- Formula
- BeAl2O4
- Hardness (Mohs)
- 8.5
- Specific gravity
- 3.67–3.83
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Orthorhombic
- Colours
- yellow, green, yellow-green, brown, colour-change green to red
- Transparency
- transparent, translucent
- Cleavage and fracture
- distinct prismatic; conchoidal to uneven fracture
- Under UV light
- alexandrite may glow weak red under UV
Typical values: real specimens vary. For more, see mindat.org.