metamorphic
Greenstone (likely serpentinite or greenstone pebble)
Serpentinite-rich ultramafic rock; commonly dominated by serpentine-group minerals, with possible chlorite, actinolite, or magnetite
AI-generated identification · may be incorrectFine-grained, rounded and polished naturally; mottled gray-green color with dull to waxy luster. Typical hardness is about 2.5–5.5 Mohs, with no visible cleavage and variable specific gravity around 2.5–2.8.
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Physical properties
Fine-grained, rounded and polished naturally; mottled gray-green color with dull to waxy luster. Typical hardness is about 2.5–5.5 Mohs, with no visible cleavage and variable specific gravity around 2.5–2.8.
Formation & geological history
Likely formed by hydration and low-temperature metamorphism of mantle-derived peridotite, commonly in oceanic crust or tectonic suture zones. Serpentinite ranges from ancient Precambrian to geologically recent formations.
Uses & applications
Used as decorative stone, carvings, tumbled specimens, aggregate, and occasionally architectural stone; attractive pieces have modest lapidary value.
Geological facts
The green color commonly comes from serpentine minerals and iron-bearing alteration products. Magnetite may make some specimens weakly magnetic.
Field identification & locations
Identify by its green mottling, soft-to-medium hardness, waxy feel, and tendency to scratch with steel; vinegar produces no reaction. Common sources include California, Italy, New Zealand, Canada, and Japan.
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