metamorphic
Tumbled dark green stone, likely serpentine
Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), possibly with magnetite or chlorite
AI-generated identification · may be incorrectDark olive-green to black, rounded and polished, with waxy-to-glassy luster and mottled patterning. Serpentine has Mohs hardness about 2.5–4, nonmetallic luster, poor cleavage, and typically massive rather than visibly crystalline structure.
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Physical properties
Dark olive-green to black, rounded and polished, with waxy-to-glassy luster and mottled patterning. Serpentine has Mohs hardness about 2.5–4, nonmetallic luster, poor cleavage, and typically massive rather than visibly crystalline structure.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during hydrothermal alteration, commonly along tectonic plate boundaries; ages range from Precambrian to recent. The pictured piece appears tumbled or polished.
Uses & applications
Used as ornamental stone, carvings, beads, and architectural facing; historically used as a decorative substitute for jade. It is mainly a collector and lapidary material rather than a high-value gemstone.
Geological facts
Serpentine can resemble nephrite jade but is generally softer and less tough. Some serpentinites contain chrysotile asbestos, so avoid cutting or generating dust unless its composition is confirmed.
Field identification & locations
Identify by its greasy/waxy feel, green-black mottling, softness, and lack of distinct crystal faces; common sources include California, Vermont, New Zealand, Italy, Canada, and Afghanistan. A scratch test and gemological analysis can distinguish it from jade.
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