igneous
Granite boulder
Granite, composed mainly of quartz, alkali feldspar, plagioclase, and minor mica/amphibole
AI-generated identification · may be incorrectCoarse-grained crystalline texture, pale gray to pinkish-white color, and generally vitreous to dull luster; hardness is approximately 6–7 Mohs, with poor cleavage as a whole and specific gravity around 2.6–2.7.
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Physical properties
Coarse-grained crystalline texture, pale gray to pinkish-white color, and generally vitreous to dull luster; hardness is approximately 6–7 Mohs, with poor cleavage as a whole and specific gravity around 2.6–2.7.
Formation & geological history
An intrusive igneous rock formed by slow cooling and crystallization of silica-rich magma deep in Earth’s crust, commonly during Precambrian to Phanerozoic mountain-building events; the rounded shape likely reflects glacial or stream abrasion.
Uses & applications
Used extensively as dimension stone, countertops, monuments, paving, aggregate, and landscaping material; attractive polished varieties are also used decoratively.
Geological facts
Granite’s visible interlocking crystals distinguish it from most sedimentary rocks and fine-grained volcanic rocks. Individual minerals may weather at different rates, producing its mottled appearance.
Field identification & locations
Identify it by its hard, speckled, interlocking crystals and lack of layering or fossils; quartz commonly appears glassy gray, while feldspar is white or pink. Common worldwide, especially in continental mountain belts and glacial deposits.
