igneous
Tumbled granite or granitic pebble
Granite; chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; rounded and polished, mottled gray-brown with visible granular crystals and earthy iron staining; vitreous to dull luster, no obvious cleavage as a whole, specific gravity roughly 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; rounded and polished, mottled gray-brown with visible granular crystals and earthy iron staining; vitreous to dull luster, no obvious cleavage as a whole, specific gravity roughly 2.6–2.8.
Formation & geological history
Slow cooling of silica-rich magma produced coarse interlocking crystals, typically during Precambrian to Phanerozoic continental crust formation; the photographed piece is naturally water-rounded or mechanically tumbled.
Uses & applications
Used as aggregate, building and paving stone, countertops, monuments, and landscaping rock; small tumbled pieces are inexpensive decor or teaching specimens.
Geological facts
Granite’s characteristic speckled appearance comes from contrasting light feldspar/quartz and dark mica or amphibole; surface staining can make it appear brown or greenish.
Field identification & locations
Identify it by its hard, granular texture and randomly interlocking light and dark minerals; common worldwide, especially in exposed continental shield and mountain regions. A definitive identification may require a fresh surface or hand lens.
