metamorphic
Serpentinite pebble
Serpentinite, composed chiefly of serpentine-group minerals (lizardite, chrysotile, antigorite), with possible magnetite and chlorite
AI-generated identification · may be incorrectDark olive-green, mottled and wet-looking with a waxy to dull luster; typically massive and fine-grained, Mohs hardness about 2.5–4, with no obvious cleavage. The rounded shape indicates water transport or tumbling.
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Physical properties
Dark olive-green, mottled and wet-looking with a waxy to dull luster; typically massive and fine-grained, Mohs hardness about 2.5–4, with no obvious cleavage. The rounded shape indicates water transport or tumbling.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite undergo hydration and low-temperature metamorphism, commonly in oceanic crust and subduction mélanges. Individual pebbles may be geologically ancient, although this specimen’s exact age cannot be determined visually.
Uses & applications
Used as decorative stone, carvings, countertops, and occasionally jewelry; it is primarily a collector specimen at this size. Chrysotile-bearing material should not be cut or abraded because its dust can be hazardous.
Geological facts
The green color comes from serpentine minerals and iron-bearing alteration products. Serpentinite is commonly associated with ophiolites and may contain magnetite, producing weak magnetism.
Field identification & locations
Look for mottled apple- to dark-green color, waxy surface, relatively low hardness, and a dense, often subtly slick texture; it can resemble jade but is generally softer. Common sources include California, Italy, New Zealand, Canada, and ophiolite belts worldwide.
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