igneous
Likely granite or granitic gneiss pebble
Granite: quartz + feldspar + mica; possibly gneiss if the minerals show layering
AI-generated identification · may be incorrectSmall rounded gray specimen with visible black-and-white granular crystals, likely quartz, feldspar, and biotite. Estimated Mohs hardness 6–7; nonmetallic luster, no obvious cleavage at this scale, and typical specific gravity around 2.6–2.8.
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Physical properties
Small rounded gray specimen with visible black-and-white granular crystals, likely quartz, feldspar, and biotite. Estimated Mohs hardness 6–7; nonmetallic luster, no obvious cleavage at this scale, and typical specific gravity around 2.6–2.8.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust; gneiss forms when such rock is metamorphosed under high pressure and temperature. The rounded shape indicates transport and weathering, likely in river or glacial deposits; precise age cannot be determined visually.
Uses & applications
Common granitic rock is widely used as crushed aggregate, road stone, building stone, paving, and monuments. This tiny pebble has minimal commercial value but may be a useful teaching or locality specimen.
Geological facts
The coarse interlocking texture records slow cooling underground. The Pyrenees near 42.9°N, 0.1°W contain abundant granitic and metamorphic rocks, making this identification regionally plausible.
Field identification & locations
Look for interlocking white/pink feldspar, translucent gray quartz, and black mica; granite is not strongly layered, whereas gneiss commonly shows bands. A hand lens and streak, hardness, and acid tests would improve confidence.
