igneous

Snowflake Obsidian

Volcanic glass (SiO2) with Cristobalite (SiO2) inclusions

Hardness: 5-5.5 | Color: Black with white-to-gray splotches | Luster: Vitreous to dull | Structure: Amorphous (non-crystalline glass) | Cleavage: Conchoidal fracture

Hardness: 5-5

Identified February 15, 2026More igneous →

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Physical properties

Hardness: 5-5.5 | Color: Black with white-to-gray splotches | Luster: Vitreous to dull | Structure: Amorphous (non-crystalline glass) | Cleavage: Conchoidal fracture

Formation & geological history

Formed through the rapid cooling of silica-rich (felsic) lava, which prevents large crystals from growing. The 'snowflakes' are spherulites of white cristobalite crystals that formed during subsequent devitrification.

Uses & applications

Predominantly used for ornamental purposes including semi-precious jewelry (beads, cabochons), carvings, and as decorative tumbling stones. Historically, obsidian was used for tools and surgical blades.

Geological facts

Despite being an igneous rock, it contains no large crystals and is technically a mineraloid. The white patterns are essentially a form of internal 'growing' of crystals within the glass over thousands of years.

Field identification & locations

Identify by its glass-like texture and characteristic white radiating patterns on a black base. Found in areas with geologically recent volcanic activity like the USA (Utah, Oregon), Mexico, and Iceland.

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Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

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Magnetite

Magnetite (Fe3O4)

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