metamorphic
Tumbled dark green stone, likely greenstone/serpentinite
Serpentinite (serpentine-group minerals, chiefly Mg₃Si₂O₅(OH)₄), possibly chlorite-rich greenstone
AI-generated identification · may be incorrectFine-grained, rounded and polished; dark green with mottled gray-green color and dull to waxy luster. Mohs hardness typically 2.5–4; massive rather than visibly crystalline, with no obvious cleavage; specific gravity about 2.5–2.7.
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Physical properties
Fine-grained, rounded and polished; dark green with mottled gray-green color and dull to waxy luster. Mohs hardness typically 2.5–4; massive rather than visibly crystalline, with no obvious cleavage; specific gravity about 2.5–2.7.
Formation & geological history
Usually forms when magnesium-rich ultramafic rocks, such as peridotite, are altered by hot, water-rich fluids during tectonic processes. Serpentinite ranges from ancient Precambrian to modern oceanic settings; the exact age cannot be determined visually.
Uses & applications
Used as ornamental stone, carvings, beads, and occasionally countertops or landscaping material; this small tumbled piece has modest decorative value.
Geological facts
Its green color commonly comes from serpentine minerals, sometimes mixed with magnetite, chlorite, or talc. It may be confused with nephrite jade, but serpentinite is generally softer and less tough.
Field identification & locations
Common in tectonically active mountain belts and ophiolite complexes, including California, Oregon, Italy, New Zealand, and Canada. A steel nail may scratch it; acid produces no reaction, and a waxy feel supports serpentinite identification.
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