igneous
Tumbled granite pebble
Granite, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, pale gray to cream with black mineral flecks; vitreous to dull luster and interlocking crystals. Hardness is about 6–7 Mohs; massive, with no consistent cleavage as a whole, and specific gravity around 2.6–2.7.
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Physical properties
Coarse-grained, pale gray to cream with black mineral flecks; vitreous to dull luster and interlocking crystals. Hardness is about 6–7 Mohs; massive, with no consistent cleavage as a whole, and specific gravity around 2.6–2.7.
Formation & geological history
An intrusive felsic igneous rock crystallized slowly from silica-rich magma deep underground, commonly during Precambrian to Phanerozoic mountain-building. The rounded shape is from natural abrasion or tumbling.
Uses & applications
Used widely for countertops, monuments, building stone, aggregate, landscaping, and decorative polished stones; it has little jewelry value except as a durable ornamental pebble.
Geological facts
The black grains are likely biotite mica or amphibole, while the light grains are feldspar and quartz. Granite’s visible crystals indicate slow underground cooling.
Field identification & locations
Identify it by its speckled interlocking texture, pale feldspar/quartz, and dark mica or amphibole; it should not fizz with dilute acid. Common worldwide, especially in continental shield and mountain regions.
