igneous
Biotite granite (likely weathered granitic rock)
Granite; chiefly quartz (SiO₂), feldspar, and biotite mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray, pink, black, and tan; glassy quartz, pale feldspar, and dark reflective mica are visible. Hardness is about 6–7 Mohs, with no strong cleavage overall; density is typically 2.6–2.7 g/cm³.
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Physical properties
Coarse-grained, speckled gray, pink, black, and tan; glassy quartz, pale feldspar, and dark reflective mica are visible. Hardness is about 6–7 Mohs, with no strong cleavage overall; density is typically 2.6–2.7 g/cm³.
Formation & geological history
A plutonic igneous rock formed when silica-rich magma cooled slowly deep underground, allowing large crystals to grow. Its exact age cannot be determined from the photograph and may range from Precambrian to recent geological periods.
Uses & applications
Used as dimension stone, countertops, paving, monuments, aggregate, and decorative landscaping material; usually has little individual collector value.
Geological facts
Granite commonly shows interlocking crystals rather than layers or vesicles. Weathering can loosen feldspar and mica, producing the rough, crumbly surface visible here.
Field identification & locations
Identify it by its coarse interlocking texture, quartz translucency, feldspar grains, and black mica flakes; it is widespread in continental mountain belts and exposed bedrock. A fresh broken surface is more diagnostic than a weathered one.
