mineral
Astrophyllite
(K,Na)3(Fe,Mn)7Ti2Si8O24(O,OH)7
AI-generated identification · may be incorrectHardness: 3-4 (Mohs). Color: Bronze-yellow to golden yellow, brown, or reddish-brown. Luster: Submetallic, pearly, or greasy. Crystal structure: Triclinic. Cleavage: Perfect in one direction. Specific gravity: 3.2-3.4.
- Hardness
- 3-4 (Mohs)
- Color
- Bronze-yellow to golden yellow, brown, or reddish-brown
- Luster
- Submetallic, pearly, or greasy
Identified More mineral →
Explore Astrophyllite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-4 (Mohs). Color: Bronze-yellow to golden yellow, brown, or reddish-brown. Luster: Submetallic, pearly, or greasy. Crystal structure: Triclinic. Cleavage: Perfect in one direction. Specific gravity: 3.2-3.4.
Formation & geological history
Forms in rare igneous rocks, typically in alkaline intrusive rocks and pegmatites. It often occurs as star-shaped aggregates of bladed crystals.
Uses & applications
Primarily collected as a mineral specimen. Sometimes cut and polished into cabochons for use in unique jewelry pieces, though its softness makes it less suitable for everyday wear rings.
Geological facts
The name astrophyllite comes from the Greek words 'astron' meaning 'star' and 'phyllon' meaning 'leaf', referring to its common star-shaped crystal habit and perfect cleavage. It is relatively rare and is most famously found in the Kola Peninsula in Russia, and in Greenland, Norway, and Colorado (USA).
Field identification & locations
Identified by its distinctive bronze to golden bladed crystals radiating in a star-like pattern within a lighter matrix, often white or grey nepheline syenite. When polished, the blades exhibit a flashy chatoyancy. Care must be taken not to confuse it with Nuummite, which has iridescent flashes in a dark matrix.
