metamorphic

Greenstone (likely serpentinite or altered basalt)

Serpentinite, chiefly serpentine-group minerals; exact identification requires testing

AI-generated identification · may be incorrect

Dark green, mottled, dull to waxy luster, massive texture, and no obvious cleavage; typical hardness is 2.5–4 Mohs, with specific gravity about 2.5–2.6. The rough surface and color are consistent with a serpentine-rich rock, though the photograph is insufficient for certainty.

Identified September 3, 2026More metamorphic →

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Physical properties

Formation & geological history

Usually forms when ultramafic mantle rocks such as peridotite are hydrated during low-temperature metamorphism; commonly associated with oceanic crust and tectonic suture zones. Its age varies widely by locality.

Uses & applications

Used as decorative stone, carvings, countertops, and lapidary material; softer pieces may be polished. Common rough specimens generally have modest commercial value.

Geological facts

Serpentinite can contain magnetite and may show weak magnetism; some varieties contain chrysotile asbestos, so avoid cutting, drilling, or generating dust until tested.

Field identification & locations

Common in California, Italy, New Zealand, Canada, and many ophiolite belts. Field clues include greasy/waxy feel, green-black mottling, relatively low hardness, and possible white veining; a streak, hardness, magnetism, and acid test would improve identification.