igneous
Snowflake Obsidian
Volcanic glass containing Spherulites of Cristobalite (SiO2)
Hardness: 5-5.5; Color: Black with white or gray patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Black with white or gray patches
- Luster
- Vitreous/Glassy
Identified More igneous →
Explore Snowflake Obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-5.5; Color: Black with white or gray patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
Formation & geological history
Formed when granitic lava cools very rapidly, preventing crystal growth. The 'snowflakes' are inclusions of cristobalite, a type of quartz that grew into radial radiating patterns as the glass partially devitrified over time.
Uses & applications
Predominantly used for jewelry (beads, cabochons), carvings, decorative ornaments, and as a popular specimen for rock collectors and metaphysical use.
Geological facts
Despite looking like a rock, obsidian is technically naturally occurring volcanic glass. The white patches are called spherulites. Ancient cultures used obsidian for making razor-sharp surgical tools and arrowheads.
Field identification & locations
Identify by the sharp conchoidal (shell-like) fracture edges and the unique pattern of white 'snowflakes' against a jet-black background. Most commonly found in areas of geologically recent volcanic activity, such as Utah (USA), Mexico, and Iceland.
