igneous
Granite
Coarse-grained granitic rock, chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled white, gray, pink, black, and greenish colors with a granular crystalline texture and vitreous-to-pearly luster. It has interlocking crystals, no regular cleavage as a rock, and specific gravity around 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; mottled white, gray, pink, black, and greenish colors with a granular crystalline texture and vitreous-to-pearly luster. It has interlocking crystals, no regular cleavage as a rock, and specific gravity around 2.6–2.7.
Formation & geological history
Forms when silica-rich magma cools slowly deep in the continental crust, allowing large crystals to grow; typical ages range from Precambrian to Cenozoic. This rounded specimen is likely weathered or tumbled granite.
Uses & applications
Widely used for countertops, monuments, building stone, paving, and aggregate; attractive polished pieces are collected but usually have modest value.
Geological facts
Visible quartz is commonly translucent gray, feldspar is white or pink, and dark flakes are biotite or amphibole. Its coarse texture distinguishes it from volcanic rhyolite.
Field identification & locations
Common worldwide, including India, Brazil, the United States, Canada, and Scandinavia. Identify it by interlocking quartz and feldspar crystals and its resistance to scratching; acid produces no reaction.
