Star ruby
Variety Al2O3
About it
Ruby cut as a cabochon to show a six-rayed star from fine rutile silk. Myanmar is the classic source; many cheap star rubies are synthetic or have a diffused surface star.
- Type
- Variety
- Group
- Corundum variety
- Formula
- Al2O3
- Hardness (Mohs)
- 9
- Specific gravity
- 3.95–4.05
- Streak
- white
- Lustre
- adamantine (diamond-like), vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- red, purplish red, pinkish red
- Transparency
- translucent, opaque
- Cleavage and fracture
- none; parting common; conchoidal to uneven fracture
- Under UV light
- often red under longwave UV
Typical values: real specimens vary. For more, see mindat.org.