metamorphic
Tumbled greenstone (likely serpentinite or green jasper)
Serpentinite, commonly dominated by serpentine-group minerals (Mg₃Si₂O₅(OH)₄); exact identification requires testing
AI-generated identification · may be incorrectOlive-green, opaque, finely grained, and waxy to vitreous when wet or polished; typically Mohs 2.5–4, with no visible crystals or cleavage and moderate density. The rounded shape indicates tumbling or natural water wear.
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Physical properties
Olive-green, opaque, finely grained, and waxy to vitreous when wet or polished; typically Mohs 2.5–4, with no visible crystals or cleavage and moderate density. The rounded shape indicates tumbling or natural water wear.
Formation & geological history
If serpentinite, it formed when ultramafic mantle rock was hydrothermally altered, commonly during oceanic crust formation and later tectonic uplift. If green jasper, it is silica-rich microcrystalline quartz formed from mineral-rich sediment or volcanic fluids; age depends on locality.
Uses & applications
Used as a decorative stone, carving material, ornamental aggregate, and collectible; some varieties are made into cabochons or beads. It has limited industrial value as a small polished specimen.
Geological facts
The image alone cannot reliably distinguish serpentinite from green jasper or other greenstone. A streak, hardness, density, and acid/microscope examination would improve identification.
Field identification & locations
Common sources include California, Oregon, Washington, New Zealand, Italy, and many ophiolite belts for serpentinite; green jasper occurs worldwide. Serpentinite scratches with a steel knife, whereas jasper generally scratches glass.
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