metamorphic
Likely tumbled serpentine or greenstone pebble
Serpentine-group minerals, chiefly antigorite/lizardite; identification is uncertain from the photo
AI-generated identification · may be incorrectSmall rounded olive-green to brown specimen with mottled coloration and a dull-to-waxy luster. Serpentine has Mohs hardness 2.5–4, poor cleavage, fine-grained or fibrous structure, and specific gravity about 2.5–2.6; the apparent pale inclusion may be quartz or carbonate.
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Physical properties
Small rounded olive-green to brown specimen with mottled coloration and a dull-to-waxy luster. Serpentine has Mohs hardness 2.5–4, poor cleavage, fine-grained or fibrous structure, and specific gravity about 2.5–2.6; the apparent pale inclusion may be quartz or carbonate.
Formation & geological history
Typically forms by low-temperature hydration and alteration of ultramafic rocks such as peridotite, commonly in oceanic crust and subduction-related metamorphic belts. Most examples are Precambrian to Phanerozoic, depending on locality.
Uses & applications
Used as a decorative stone, carving material, ornamental aggregate, and historically as a source of asbestos-type fibers; attractive polished pieces are collected but generally inexpensive.
Geological facts
Serpentine is often mistaken for jade because of its green color, but it is softer and commonly more waxy. Fibrous varieties should not be cut, drilled, or abraded because inhaled dust can be hazardous.
Field identification & locations
Field clues include olive-green mottling, waxy feel, low hardness, and alteration veins; it may scratch with a steel knife but not glass. Common sources include California, Italy, New Zealand, Canada, and Afghanistan.
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