igneous
Granite boulder
Granite; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray rock with visible interlocking crystals; quartz and feldspar give a glassy to dull luster, while mica appears dark. Mohs hardness is about 6–7; cleavage is weak to absent as a rock, and typical specific gravity is 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray rock with visible interlocking crystals; quartz and feldspar give a glassy to dull luster, while mica appears dark. Mohs hardness is about 6–7; cleavage is weak to absent as a rock, and typical specific gravity is 2.63–2.75.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly deep underground, allowing large crystals to grow. Its exact geological age cannot be determined from the photograph and may range from Precambrian to much younger depending on location.
Uses & applications
Widely used for building stone, monuments, countertops, paving, aggregate, and landscaping; attractive polished pieces may be used decoratively.
Geological facts
Granite commonly develops rounded weathering surfaces and may contain dark biotite or hornblende. The specimen appears naturally weathered and may be a glacially transported or locally exposed boulder.
Field identification & locations
Identify it by its coarse interlocking quartz-feldspar-mica texture and lack of layering or foliation; distinguish it from finer-grained volcanic rocks. Common worldwide in continental crust and granite plutons.
