Foitite
Mineral □(Fe2Al)Al6(Si6O18)(BO3)3(OH)3(OH)
About it
A sodium-poor iron tourmaline, bluish black and looking like schorl, known from the Pala district pegmatites of southern California and the Urals; telling it from schorl needs analysis.
- Type
- Mineral
- Group
- Silicate (cyclosilicate), tourmaline group
- Formula
- □(Fe2Al)Al6(Si6O18)(BO3)3(OH)3(OH)
- Hardness (Mohs)
- 7
- Specific gravity
- 3.17
- Streak
- greyish white
- Lustre
- vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- bluish black, black
- Transparency
- opaque
- Cleavage and fracture
- none; irregular fracture
Typical values: real specimens vary. For more, see mindat.org.