igneous
Snowflake Obsidian
Volcanic Glass (SiO2 with Cristobalite inclusions)
Hardness: 5-5.5 on Mohs scale. Color: Black background with white/gray snowflake-like patches. Luster: Vitreous to shiny when polished. Fracture: Conchoidal. Crystal structure: Amorphous glass matrix containing microcrystalline cristobalite spherulites.
- Hardness
- 5-5
- Color
- Black background with white/gray snowflake-like patches
- Luster
- Vitreous to shiny when polished
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 on Mohs scale. Color: Black background with white/gray snowflake-like patches. Luster: Vitreous to shiny when polished. Fracture: Conchoidal. Crystal structure: Amorphous glass matrix containing microcrystalline cristobalite spherulites.
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth, creating natural glass. Over time, devitrification occurs where parts of the glass recrystallize into cristobalite (a silica polymorph), forming the distinctive white radial snowflake patterns.
Uses & applications
Used extensively in jewelry, lapidary art, polished tumbled stones, cabochons, decorative carvings, and as a popular specimen for rock collectors. Historically, obsidian was used for sharp tools and arrowheads.
Geological facts
The white patches in snowflake obsidian are composed of cristobalite inclusions formed through a process called devitrification, where amorphous volcanic glass slowly transforms into crystalline mineral structures over geological time.
Field identification & locations
Identified by its jet-black glassy base with distinct white or pale gray snowflake-like spots. Commonly found in volcanic regions worldwide including the western United States (Utah, Oregon, California), Mexico, Iceland, and Japan.
