metamorphic
Rounded dark metamorphic pebble
Likely mica schist or chlorite-rich greenschist; exact identification requires testing
AI-generated identification · may be incorrectDark gray-green, fine to medium grained, dull to slightly silky luster, and water-worn/rounded. Likely hardness about 3–6 depending on mica and quartz content; cleavage or foliation may be obscured by weathering and abrasion.
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Physical properties
Dark gray-green, fine to medium grained, dull to slightly silky luster, and water-worn/rounded. Likely hardness about 3–6 depending on mica and quartz content; cleavage or foliation may be obscured by weathering and abrasion.
Formation & geological history
Probably a river or glacially transported metamorphic fragment, with foliation developed during regional metamorphism. Around 42.9°N, 0.1°W in the Pyrenees, metamorphic rocks are geologically plausible; age may range from Paleozoic to Mesozoic depending on source unit.
Uses & applications
Primarily a natural collecting specimen or decorative pebble; not identifiable as a commercial gemstone from the photograph.
Geological facts
The pale reflective flecks may be mica, while the greenish tone could indicate chlorite. A streak, fresh broken surface, hardness test, and hand lens would distinguish schist from dark volcanic rocks such as basalt.
Field identification & locations
Commonly found in Pyrenean streams and scree derived from metamorphic terranes. Check for visible layered foliation, mica flakes, and a gray-white streak; avoid acid testing unless carbonate veins are suspected.
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