igneous
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)
Hardness: 5-5.5 on Mohs scale; Color: Black with grayish-white 'snowflake' 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 grayish-white 'snowflake' patches
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 on Mohs scale; Color: Black with grayish-white 'snowflake' patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6.
Formation & geological history
Formed through the rapid cooling of silica-rich felsic lava. The 'snowflakes' are inclusions of the mineral cristobalite (a type of quartz) that formed as the glass began to devitrify over time. Most specimens are from the Neogene or Quaternary periods.
Uses & applications
Commonly used in jewelry (cabochons, beads), decorative carvings, meditation stones, and as a collector's mineral due to its unique aesthetics.
Geological facts
While regular obsidian is considered a volcanic glass, the white patches in Snowflake Obsidian represent the 'death' of the glass, as it is slowly crystallizing into quartz minerals. Historically, obsidian was used by indigenous peoples for extremely sharp cutting tools and arrowheads.
Field identification & locations
Identify by its distinctive white radial 'snowflake' patterns against a jet-black glassy background. It is found in volcanic regions, notably in Utah (USA), Mexico, and Iceland. In the field, look for smooth, glassy textures and sharp, curved edges on broken pieces.
