igneous
Biotite granite (likely weathered)
Granite, composed mainly of quartz, potassium feldspar, plagioclase, and biotite mica
AI-generated identification · may be incorrectTypically coarse-grained, gray to pink, with visible dark mica and glassy quartz; hardness about 6–7 Mohs, vitreous to pearly luster, no dominant cleavage as a whole, specific gravity about 2.6–2.7.
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Physical properties
Typically coarse-grained, gray to pink, with visible dark mica and glassy quartz; hardness about 6–7 Mohs, vitreous to pearly luster, no dominant cleavage as a whole, specific gravity about 2.6–2.7.
Formation & geological history
A plutonic igneous rock crystallized slowly from silica-rich magma deep in Earth’s crust, commonly during Precambrian to recent continental mountain-building events; the specimen appears weathered and possibly iron-stained.
Uses & applications
Widely used as building stone, countertops, monuments, curbing, aggregate, and decorative landscaping rock; ordinary hand specimens have little jewelry value.
Geological facts
Its coarse texture records slow underground cooling, allowing large interlocking crystals to form. Dark flakes are likely biotite, while translucent grains are quartz.
Field identification & locations
Identify it by its interlocking visible crystals, abundant light feldspar/quartz, and black or brown mica flakes; common worldwide in continental shields and mountain belts. A hand lens and scratch test help distinguish it from basalt or gneiss.
