igneous
Polished black gemstone carving, likely obsidian
Volcanic glass (primarily SiO₂), commonly called obsidian
AI-generated identification · may be incorrectTypically black, vitreous to glassy luster, opaque, and lacking visible crystals; Mohs hardness about 5–5.5, conchoidal fracture, and no cleavage. The strongly curved, polished shape appears carved rather than naturally crystallized.
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Physical properties
Typically black, vitreous to glassy luster, opaque, and lacking visible crystals; Mohs hardness about 5–5.5, conchoidal fracture, and no cleavage. The strongly curved, polished shape appears carved rather than naturally crystallized.
Formation & geological history
Obsidian forms when silica-rich lava cools rapidly enough to prevent crystal growth, generally in young volcanic regions, often from Quaternary to recent eruptions. Common sources include Mexico, the western United States, Armenia, Turkey, and Iceland.
Uses & applications
Used for carvings, cabochons, jewelry, ornaments, and historically razor-sharp tools and arrowheads. Its value is mainly decorative and depends on polish, design, and confirmed material.
Geological facts
The specimen could also be black onyx, jet, or another dark stone; the image alone cannot confirm composition. Obsidian commonly shows sharp conchoidal edges and may display sheen, snowflake, or rainbow effects.
Field identification & locations
A glassy appearance, very smooth polish, uniform black color, and conchoidal-looking edges support obsidian; it should not scratch ordinary glass easily if heavily polished. A hardness, specific-gravity, or refractive-index test can distinguish it from jet or plastic.
