metamorphic
Tumbled serpentine-rich stone (likely serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, chlorite, and carbonate
AI-generated identification · may be incorrectTypically olive-green to dark green, mottled, waxy to subvitreous luster, fine-grained and massive; Mohs hardness about 2.5–4, with no obvious cleavage and specific gravity around 2.5–2.6. The rounded shape indicates human tumbling and polishing.
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Physical properties
Typically olive-green to dark green, mottled, waxy to subvitreous luster, fine-grained and massive; Mohs hardness about 2.5–4, with no obvious cleavage and specific gravity around 2.5–2.6. The rounded shape indicates human tumbling and polishing.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during metamorphism, commonly in ancient oceanic crust and subduction zones. Individual pieces may range from Precambrian to recent tectonic settings; age cannot be determined visually.
Uses & applications
Used as a decorative carving and cabochon material, ornamental stone, and occasionally architectural stone. Common specimens generally have modest collector value.
Geological facts
Serpentinite’s green coloration results from hydration and alteration of olivine- and pyroxene-rich rocks. Some varieties contain asbestos-form serpentine minerals, so avoid cutting, drilling, or generating dust unless its composition is confirmed.
Field identification & locations
Common in California, Italy, New Zealand, Canada, and ophiolite belts worldwide. Field clues include greasy or waxy feel, mottled green-black color, low hardness, and possible magnetism; acid reaction is usually absent unless carbonate is present.
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