igneous
Tumbled granite or granitic gneiss
Granite/granitic gneiss, chiefly quartz, feldspar, and dark mica or amphibole
AI-generated identification · may be incorrectCoarse crystalline, pale gray to greenish-white with black mineral patches; glassy to dull luster, no obvious cleavage, Mohs hardness about 6–7, and typical specific gravity 2.6–2.8. Its rounded shape indicates natural water abrasion or tumbling.
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Physical properties
Coarse crystalline, pale gray to greenish-white with black mineral patches; glassy to dull luster, no obvious cleavage, Mohs hardness about 6–7, and typical specific gravity 2.6–2.8. Its rounded shape indicates natural water abrasion or tumbling.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust; granitic gneiss is its metamorphosed equivalent, formed during ancient mountain-building. The exact geological age and identity cannot be determined from the photograph.
Uses & applications
Used widely as building stone, aggregate, monuments, countertops, and landscaping rock; attractive polished pieces are collected but rarely valuable.
Geological facts
The dark patches are likely biotite mica or hornblende, while translucent/light grains are quartz and feldspar. A streak, acid test, and close inspection of grain boundaries can distinguish granite from gneiss or other pale metamorphic rocks.
Field identification & locations
Common in continental shields, mountain belts, glacial deposits, streambeds, and beaches worldwide; identify by visible interlocking grains and mixed light/dark minerals rather than layers or fossils.
