igneous
Black polished gemstone pendant, likely obsidian
Volcanic glass; primarily SiO₂ (noncrystalline), possibly black spinel or dyed quartz
AI-generated identification · may be incorrectUsually black to dark gray with vitreous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5; the image alone cannot confirm composition. The faceted, translucent-edged appearance is consistent with polished obsidian but may also indicate another dark gemstone.
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Physical properties
Usually black to dark gray with vitreous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5; the image alone cannot confirm composition. The faceted, translucent-edged appearance is consistent with polished obsidian but may also indicate another dark gemstone.
Formation & geological history
Obsidian forms when silica-rich lava cools rapidly, preventing crystal growth, generally in geologically young volcanic regions. Common sources include Mexico, the western United States, Armenia, Turkey, and Japan.
Uses & applications
Used for jewelry, ornaments, carvings, and historically sharp tools and blades; this specimen is mounted as a pendant. Value is mainly determined by material identity, transparency, finish, and workmanship.
Geological facts
Obsidian is technically volcanic glass rather than a crystalline mineral. It may show sheen, snowflake patterns, or rainbow colors caused by microscopic inclusions or flow textures.
Field identification & locations
Check for glassy luster, conchoidal fracture, and lack of visible crystals; a streak, hardness, refractive-index, or specific-gravity test is needed for confirmation. Similar black spinel, tourmaline, onyx, and dyed glass can look nearly identical.
