igneous
Granite
Coarse-grained felsic intrusive igneous rock, chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectTypically white to gray and speckled, with visible interlocking crystals and a granular texture; hardness about 6–7 Mohs, vitreous quartz luster, no cleavage as a rock, and specific gravity roughly 2.6–2.7.
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Physical properties
Typically white to gray and speckled, with visible interlocking crystals and a granular texture; hardness about 6–7 Mohs, vitreous quartz luster, no cleavage as a rock, and specific gravity roughly 2.6–2.7.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep within continental crust, commonly during Precambrian to Phanerozoic mountain-building events; the pictured piece may also be granitic gneiss or weathered granodiorite.
Uses & applications
Widely used for countertops, monuments, building stone, paving, and aggregate; attractive polished pieces are collected but are usually low value.
Geological facts
The light minerals are likely quartz and feldspar, while dark flecks are biotite or amphibole. Its coarse crystals indicate slow underground cooling rather than volcanic eruption.
Field identification & locations
Identify it by its hard, crystalline, salt-and-pepper appearance and inability to scratch easily with a steel knife; distinguish it from gneiss by the lack of strong mineral banding. Common worldwide in continental shields and mountain belts.
