igneous
Tumbled-looking granite pebble
Granite, chiefly quartz–feldspar with biotite/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale cream to gray, with black mafic specks and a granular texture. Crystalline structure, generally massive, with no prominent cleavage; typical specific gravity is 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; pale cream to gray, with black mafic specks and a granular texture. Crystalline structure, generally massive, with no prominent cleavage; typical specific gravity is 2.6–2.7.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly underground, allowing visible crystals to grow; commonly Precambrian to Phanerozoic in age. The rounded shape likely resulted from stream abrasion.
Uses & applications
Used as crushed aggregate, building stone, paving, monuments, and decorative material; attractive polished pieces are collected but have modest value.
Geological facts
The cream color is likely potassium feldspar and/or weathered plagioclase, while the dark grains are biotite or amphibole; quartz may appear as translucent gray grains.
Field identification & locations
Common in continental crust and streambeds derived from granite outcrops worldwide. Identify it by its interlocking crystalline grains, feldspar-rich pale matrix, quartz, and scattered black minerals; a glassy or uniformly colored surface would suggest another material.
