igneous

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)

Hardness: 5-5.5 on Mohs scale; Color: Black with white or gray flower-like 'snowflakes'; Luster: Vitreous (glassy); Crystal Structure: Amorphous (glass); Cleavage: Conchoidal fracture; Specific Gravity: 2.3 - 2.6.

Hardness: 5-5
Color: Black with white or gray flower-like 'snowflakes'
Luster: Vitreous (glassy)

Identified March 25, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the rapid cooling of felsic lava. As the glass begins to devitrify over geological time, needle-like crystals of cristobalite form radiating patterns known as spherulites, which create the white 'snowflake' appearance.

Uses & applications

Commonly used for lapidary work, jewelry (beads and cabochons), small carvings, and as a popular teaching specimen for geology students.

Geological facts

Unlike minerals, obsidian is a 'mineraloid' because it lacks a crystalline structure. The 'snowflakes' are actually internal crystals of cristobalite, a type of quartz that grows as the glass cools or ages.

Field identification & locations

Identify by its glass-like texture and prominent white splotches on a jet-black background. It is commonly found in areas of recent volcanic activity such as Utah, USA, and parts of Mexico. Collectors should look for sharp conchoidal edges on unpolished pieces.

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Dark Igneous Rock (Likely Basalt or Diabase)

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.

Igneous

Magnetite

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Magnetite

Magnetite (Fe3O4)

mineral