igneous
Black Obsidian
Volcanic Glass (SiO2 with impurities)
Hardness 5-5.5 on Mohs scale, deep black color, vitreous/glassy luster, amorphous crystal structure, no cleavage with conchoidal fracture.
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Physical properties
Hardness 5-5.5 on Mohs scale, deep black color, vitreous/glassy luster, amorphous crystal structure, no cleavage with conchoidal fracture.
Formation & geological history
Extrusive igneous rock formed when felsic lava cools rapidly with minimal crystal growth.
Uses & applications
Used in jewelry making, beadwork, surgical scalpel blades, ornamental carvings, and gemstone collection.
Geological facts
Obsidian fractures with extremely sharp edges, making it a historically crucial material for tools and arrowheads long before modern steel.
Field identification & locations
Identify by its glassy luster, dark opaque appearance, smooth conchoidal fracture, and lightweight feel relative to metallic stones.
