Kornerupine
Mineral (Mg,Fe,Al)10(Si,Al,B)5O21(OH,F)
About it
A rare gem species, green to brown with strong colour change by direction; Kenya, Madagascar, Sri Lanka, and Tanzania. Named for Greenland explorer Andreas Kornerup.
- Type
- Mineral
- Group
- Silicate (sorosilicate), prismatine group
- Formula
- (Mg,Fe,Al)10(Si,Al,B)5O21(OH,F)
- Hardness (Mohs)
- 6–7
- Specific gravity
- 3.29–3.35
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Orthorhombic
- Colours
- green, brown, yellow, blue, colourless, black
- Transparency
- transparent, translucent
- Cleavage and fracture
- good in two directions
Typical values: real specimens vary. For more, see mindat.org.