igneous
Biotite granite (likely weathered)
Granite; quartz–alkali feldspar–plagioclase–biotite aggregate
AI-generated identification · may be incorrectCoarse-grained, speckled brown, cream, and dark minerals with vitreous quartz and feldspar, plus reflective black-brown biotite mica; hardness about 6–7 overall, no dominant cleavage, and granular crystalline texture.
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Physical properties
Coarse-grained, speckled brown, cream, and dark minerals with vitreous quartz and feldspar, plus reflective black-brown biotite mica; hardness about 6–7 overall, no dominant cleavage, and granular crystalline texture.
Formation & geological history
A felsic intrusive igneous rock crystallized slowly from silica-rich magma several kilometers underground, typically during Precambrian or younger continental mountain-building events; brown coloration may reflect weathering or iron oxidation.
Uses & applications
Widely used as dimension stone, countertops, paving, monuments, building façades, and crushed aggregate; attractive polished pieces have modest decorative and collecting value.
Geological facts
Its interlocking crystals are characteristic of slow underground cooling. Biotite commonly weathers to rusty brown clay minerals, making exposed granite appear mottled or stained.
Field identification & locations
Identify by visible interlocking quartz, pale feldspar, and dark mica; it is common in continental shields and mountain belts worldwide, including India, Brazil, Scandinavia, and North America. A hand lens and streak/acid tests help distinguish it from gneiss or diorite.
