metamorphic
Greenstone pebble (likely altered basalt/serpentinite)
Chlorite–epidote amphibolite or serpentinized mafic rock; exact identification requires testing
AI-generated identification · may be incorrectDark green, fine-grained, subrounded and water-worn, with rusty orange-brown iron-oxide staining and a small fracture. Likely Mohs 5–6 (lower if serpentinized), dull to faintly waxy luster, massive texture, and no obvious cleavage.
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Physical properties
Dark green, fine-grained, subrounded and water-worn, with rusty orange-brown iron-oxide staining and a small fracture. Likely Mohs 5–6 (lower if serpentinized), dull to faintly waxy luster, massive texture, and no obvious cleavage.
Formation & geological history
Probably a stream or beach pebble derived from metamorphosed or hydrothermally altered basalt/gabbro; iron-bearing minerals weathered to limonite/goethite. Its precise geological age and locality cannot be determined from the image.
Uses & applications
Usually valued as a field or decorative specimen; greenstone may be polished for cabochons, carvings, and landscaping, while related serpentinite is used as ornamental stone.
Geological facts
The green color commonly comes from chlorite, epidote, actinolite, or serpentine, whereas the orange patches indicate oxidation of iron. The smooth shape reflects prolonged abrasion in moving water.
Field identification & locations
Look for a dense, fine-grained green body, rusty weathering, and possible magnetic response; a streak, hardness, acid, and thin-section test can distinguish basaltic greenstone from serpentinite. Common in streams draining volcanic or metamorphic terrains.
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