mineral

Astrophyllite

Potassium Sodium Iron Manganese Titanium Silicate Hydroxide (K3NaFe7Ti2Si8O24(OH)7)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: Golden-brown to bronze-yellow sprays in a dark (often black or grey) matrix; Luster: Submetallic, pearly; Crystal Structure: Triclinic with bladed, radiating 'star' shapes; Cleavage: Perfect in one direction; Specific Gravity: 3.3-3.4

Hardness: 3-4 (Mohs)
Luster: Submetallic, pearly

Identified March 16, 2026More mineral →

Explore Astrophyllite in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in unusual, rare alkaline igneous rocks (nepheline syenites and pegmatites). Most specimens were formed during volcanic activity in the Cenozoic or Paleozoic eras depending on the specific alkaline massif locality.

Uses & applications

Primarily used as a collector mineral and in ornamental jewelry/lapidary work. It is valued for its unique 'star' or 'firework' patterns when cut into cabochons.

Geological facts

The name comes from the Greek words 'astron' for star and 'phyllon' for leaf, referring to its leaf-like cleavage and star-like radiating crystals. It is chemically related to micas but has a significantly different crystal structure.

Field identification & locations

Identify by its distinctive bronze-colored, bladed radiating crystals embedded in a dark matrix. Principal localities include the Kola Peninsula in Russia, Mont Saint-Hilaire in Quebec, and parts of Greenland and Norway. For collectors, it is easily distinguished from Arfvedsonite and Bronzite by its specific titanium content and crystal habit.