igneous
Snowflake Obsidian
Spherulitic Obsidian (Volcanic Glass with Cristobalite inclusions)
Hardness: 5-5.5 | Color: Smooth black glass with white or grayish flower-like patches | Luster: Vitreous (glassy) | Crystal Structure: Amorphous (non-crystalline glass) | Cleavage: None (conchoidal fracture) | SG: 2.35-2.60
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 | Color: Smooth black glass with white or grayish flower-like patches | Luster: Vitreous (glassy) | Crystal Structure: Amorphous (non-crystalline glass) | Cleavage: None (conchoidal fracture) | SG: 2.35-2.60
Formation & geological history
Formed through the rapid cooling of felsic (silica-rich) lava. The white 'snowflakes' are spherulites of cristobalite, which form during the devitrification process over millions of years.
Uses & applications
Primarily used for lapidary work, jewelry (beads, cabochons), ornamental carvings, and by collectors. Historically used for sharp tools due to its conchoidal fracture.
Geological facts
Obsidian is not a mineral because it lacks a crystalline structure; it is a mineraloid. The 'snowflakes' are actually internal crystals that began to grow as the glass slowly decayed over geological time.
Field identification & locations
Identify by its glassy black base and unique white radial patterns. Often found in volcanic areas such as the Western USA (Utah, California), Mexico, and Iceland. Look for its characteristic shell-like fracture pattern.
