igneous
Gray granite (likely weathered granite or granitic gneiss)
Granite; chiefly quartz, feldspar, and mica (typically ~20–60% quartz)
AI-generated identification · may be incorrectHardness about 6–7 Mohs; gray, medium-grained, granular texture with subdued vitreous to dull luster. Interlocking quartz and feldspar crystals are visible, with minor dark mica; cleavage occurs in feldspar, not as a whole rock.
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Physical properties
Hardness about 6–7 Mohs; gray, medium-grained, granular texture with subdued vitreous to dull luster. Interlocking quartz and feldspar crystals are visible, with minor dark mica; cleavage occurs in feldspar, not as a whole rock.
Formation & geological history
Formed by slow crystallization of silica-rich magma several kilometers underground, generally during Precambrian to Phanerozoic continental crust formation. Surface weathering has dulled the exposed face.
Uses & applications
Widely used for building stone, monuments, countertops, paving, curbs, and crushed aggregate; attractive polished varieties are used decoratively. Common specimens have little collector value.
Geological facts
Granite is intrusive and typically displays no layering or vesicles; pink, white, or gray feldspar and scattered black mica help distinguish it from basalt. The image may also represent a granitic gneiss if faint foliation is present.
Field identification & locations
Common in continental mountain belts and shield regions worldwide, including New England, the Canadian Shield, Scandinavia, India, and the Sierra Nevada. Identify it by its hard, speckled, interlocking crystals and inability to scratch with a steel knife.
