metamorphic
Serpentinite pebble
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with magnetite and accessory chlorite/talc
AI-generated identification · may be incorrectTypically dark green to black, mottled and waxy to greasy, with locally sparkly or earthy surfaces; hardness about 2.5–4, Mohs, low-to-moderate luster, and no consistent cleavage. The rounded shape indicates water-worn pebble or tumbling, and the pale green/yellow patches are characteristic serpentine alteration.
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Physical properties
Typically dark green to black, mottled and waxy to greasy, with locally sparkly or earthy surfaces; hardness about 2.5–4, Mohs, low-to-moderate luster, and no consistent cleavage. The rounded shape indicates water-worn pebble or tumbling, and the pale green/yellow patches are characteristic serpentine alteration.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during seafloor spreading, subduction, or faulting; individual specimens may range from Precambrian to modern tectonic settings. Common in ophiolite belts and active or ancient mountain-building zones.
Uses & applications
Used as decorative stone, carvings, countertops, and ornamental aggregate; attractive varieties are collected and occasionally marketed as “new jade,” though they are not jadeite or nephrite.
Geological facts
Serpentinite commonly contains magnetite, making some pieces weakly magnetic, and may host asbestos-forming minerals; avoid cutting or generating dust unless professionally tested. Its green color results from hydrothermal alteration of olivine- and pyroxene-rich rocks.
Field identification & locations
Look for mottled green-black color, soft waxy texture, fine grain, and possible magnetism; common sources include California, Italy, New Zealand, Canada, and ophiolite regions worldwide. The image alone cannot exclude related rocks such as chlorite-rich metamorphic rock.
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