igneous

Snowflake Obsidian

Volcanic glass containing Spherulites (SiO2)

Hardness: 5.0-5.5 (Mohs scale); Color: Black with white-to-grayish patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline matrix); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.3-2.6

Hardness: 5
Color: Black with white-to-grayish patches
Luster: Vitreous/Glassy

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed from rapidly cooling felsic lava where water and impurities were present. The internal crystal 'snowflakes' are spherulites of cristobalite (a silica mineral) that grew during the partial devitrification of the glass.

Uses & applications

Predominantly used for ornamental purposes, including beads, jewelry, cabochons, and decorative carvings. Historically, obsidian was used for making sharp blades and arrowheads.

Geological facts

Despite being an igneous rock, it is often referred to as a mineraloid because it lacks a crystalline structure. The 'snowflakes' result from the chemical process of devitrification, where the glass starts to crystallize over vast periods of time.

Field identification & locations

Identify by its characteristic white radial inclusions on a black glassy surface and smooth, shell-like fracture pattern. Commonly found in volcanic regions such as the United States (Utah and Oregon), Mexico, and Iceland.

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