igneous
Obsidian (Apache Tear)
Volcanic Glass (High-silica Rhyolite)
Hardness: 5-5.5 (Mohs scale); Color: Black to dark smoky brown; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Black to dark smoky brown
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black to dark smoky brown; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
Formation & geological history
Formed through the rapid cooling of silica-rich (rhyolitic) lava, so fast that crystals could not grow. These rounded 'Apache Tears' specimens are often found embedded in greyish perlite matrices.
Uses & applications
Used for making jewelry (cabochons), ornamental carvings, and historically for sharp tools like arrowheads and scalpel blades due to its razor-sharp edges.
Geological facts
Obsidian is not a mineral because it lacks a crystalline structure; it is an amorphous volcanic glass. 'Apache Tears' are named after a legend concerning grieving Apache women following a battle in Arizona.
Field identification & locations
Identified by its jet-black color, glassy surface, and distinct curved (conchoidal) fractures. Tumbled versions like this are smooth and highly reflective. Common in volcanic regions like the American Southwest, Mexico, and Iceland.
