igneous
Likely gray granite fragment
Granite, composed mainly of quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray-and-white appearance with a possible mica sheen; hardness about 6–7 Mohs, vitreous to pearly luster, interlocking crystalline texture, and poor cleavage as a whole rock.
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Physical properties
Coarse-grained, speckled gray-and-white appearance with a possible mica sheen; hardness about 6–7 Mohs, vitreous to pearly luster, interlocking crystalline texture, and poor cleavage as a whole rock.
Formation & geological history
Forms when silica-rich magma cools slowly underground, allowing large crystals to grow, typically during Precambrian to Phanerozoic continental mountain-building. The small angular piece appears weathered or broken from a larger outcrop or building stone.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and decorative specimens; this small fragment has little commercial value.
Geological facts
Granite’s visible grains are usually quartz, potassium feldspar, plagioclase, and biotite or muscovite. The dark mineral may be biotite or amphibole, but the photograph is insufficient for precise identification.
Field identification & locations
Identify it by its coarse interlocking grains, mixed light and dark minerals, and inability to fizz strongly in dilute acid. Common worldwide, especially in continental shields and mountain belts; a hand lens and streak test help distinguish it from basalt or gneiss.
