igneous
Granite
Granite; primarily quartz, feldspar, and mica (commonly biotite)
AI-generated identification · may be incorrectCoarse-grained, speckled gray-and-pink rock with black mica; vitreous quartz and pearly feldspar luster, interlocking crystals, no foliation, Mohs hardness about 6–7, and specific gravity roughly 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray-and-pink rock with black mica; vitreous quartz and pearly feldspar luster, interlocking crystals, no foliation, Mohs hardness about 6–7, and specific gravity roughly 2.63–2.75.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly deep underground, allowing large crystals to grow; most examples formed during Precambrian to Phanerozoic continental crust formation.
Uses & applications
Widely used for countertops, monuments, building stone, paving, aggregate, and decorative polished slabs; attractive specimens have modest collecting value.
Geological facts
The image shows a rounded, weathered cobble, likely transported by glacial or stream action; dark bands may reflect biotite-rich mineral concentrations or minor gneissic-looking variation.
Field identification & locations
Identify it by visible quartz, light feldspar, and black mica in a coarse interlocking texture; common worldwide, especially in continental shields, mountain belts, and granitic batholiths.
