igneous
Granite (likely biotite granite)
Coarse-grained felsic plutonic rock composed mainly of quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectVisible interlocking crystals; upper specimen is dark gray and lower specimen pink-brown with black mica. Mohs hardness about 6–7, vitreous to dull luster, granular texture, no cleavage as a rock, and density roughly 2.6–2.8 g/cm³.
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Physical properties
Visible interlocking crystals; upper specimen is dark gray and lower specimen pink-brown with black mica. Mohs hardness about 6–7, vitreous to dull luster, granular texture, no cleavage as a rock, and density roughly 2.6–2.8 g/cm³.
Formation & geological history
Forms when silica-rich magma cools slowly deep underground, producing large crystals; specimens may range from Precambrian to younger Mesozoic–Cenozoic plutons depending on locality.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and decorative landscaping material; attractive pieces are collected but are rarely gem-grade.
Geological facts
Granite’s mineral proportions and grain size create its familiar speckled appearance; pink color commonly reflects potassium feldspar, while dark grains are biotite or hornblende.
Field identification & locations
Identify it by coarse interlocking quartz and feldspar grains, abundant feldspar, and hardness sufficient to scratch glass; common worldwide in continental mountain belts and exposed plutons.
