Astrophyllite
Mineral K2NaFe7Ti2Si8O28(OH)4F
About it
Bronze-gold, flattened blades in starburst sprays with a submetallic sheen; Kola Peninsula, Russia, Mont Saint-Hilaire, Quebec, and St. Peters Dome, Colorado.
- Type
- Mineral
- Group
- Silicate (inosilicate), astrophyllite group
- Formula
- K2NaFe7Ti2Si8O28(OH)4F
- Hardness (Mohs)
- 3–3.5
- Specific gravity
- 3.2–3.4
- Streak
- golden yellow
- Lustre
- submetallic, pearly, greasy
- Crystal system
- Triclinic
- Colours
- bronze yellow, golden brown, reddish brown
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- perfect in one direction, brittle flakes
Typical values: real specimens vary. For more, see mindat.org.