igneous
Weathered granitoid rock
Granite or granitic gneiss; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse, granular texture with tan, pink, gray, and dark mineral grains; likely Mohs 6–7, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity about 2.6–2.8. The rounded edges and subdued surface indicate weathering or abrasion.
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Physical properties
Coarse, granular texture with tan, pink, gray, and dark mineral grains; likely Mohs 6–7, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity about 2.6–2.8. The rounded edges and subdued surface indicate weathering or abrasion.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep underground, commonly during Precambrian to younger continental crust formation; if foliation is present, it may be gneiss. Exact age and identity require a fresh surface or testing.
Uses & applications
Granite is widely used as building stone, countertops, monuments, aggregate, and landscaping material; ordinary specimens have little jewelry value.
Geological facts
Visible speckling reflects interlocking quartz, feldspar, and mica crystals. Iron-bearing minerals may weather to the rusty brown coating seen here.
Field identification & locations
Common in continental mountain belts and glacial deposits worldwide; identify by coarse interlocking grains, pale feldspar/quartz, and dark mica or amphibole. A streak, acid test, hand lens, and hardness test can refine identification.
