metamorphic
Weathered greenstone (probable serpentinite)
Serpentinite, dominated by serpentine-group minerals (antigorite/lizardite/chrysotile), with possible magnetite and iron oxides
AI-generated identification · may be incorrectHardness about 2.5–4 Mohs; mottled olive-green, brown, and rusty-red surface with dull to waxy luster. Typically massive and fine-grained rather than visibly crystalline; cleavage is poor or absent, and specific gravity is commonly about 2.5–2.6.
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Physical properties
Hardness about 2.5–4 Mohs; mottled olive-green, brown, and rusty-red surface with dull to waxy luster. Typically massive and fine-grained rather than visibly crystalline; cleavage is poor or absent, and specific gravity is commonly about 2.5–2.6.
Formation & geological history
Forms when magnesium-rich ultramafic rocks such as peridotite are hydrated during metamorphism, commonly in oceanic crust and subduction-zone settings. The exact age cannot be determined from the photograph.
Uses & applications
Used as decorative or carving stone, aggregate, and occasionally ornamental “serpentine” in jewelry; attractive polished pieces may be collectible.
Geological facts
The brown-red colors are likely iron-oxide weathering, while the green areas suggest serpentine minerals. Some serpentinite can contain asbestos-form chrysotile, so avoid cutting, sanding, or generating dust.
Field identification & locations
Likely serpentinite if it feels unusually smooth/waxy, is relatively soft, and shows a green mottled interior; a hardness, streak, density, and magnetism test would help confirm it. Common in California, Italy, New Zealand, Canada, and many ancient ophiolite belts.
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