igneous
Granite
Granite; primarily quartz (SiO₂), potassium feldspar, plagioclase feldspar, and biotite/amphibole
AI-generated identification · may be incorrectCoarse-grained, light gray to pink rock with conspicuous black mafic minerals; vitreous quartz and blocky feldspar crystals, no foliation. Mohs hardness about 6–7; high durability and specific gravity roughly 2.6–2.8.
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Physical properties
Coarse-grained, light gray to pink rock with conspicuous black mafic minerals; vitreous quartz and blocky feldspar crystals, no foliation. Mohs hardness about 6–7; high durability and specific gravity roughly 2.6–2.8.
Formation & geological history
An intrusive felsic igneous rock formed by slow cooling and crystallization of silica-rich magma deep within the continental crust, commonly during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and building cladding; attractive polished pieces are collected but ordinary cobbles have little commercial value.
Geological facts
The rounded specimens are likely weathered granite cobbles, with rounding produced by transport in streams or glacial deposits. Dark spots are biotite or amphibole, while pale grains are feldspar and quartz.
Field identification & locations
Identify it by its visibly interlocking, coarse crystals and lack of layering; a glassy quartz grain, feldspar, and dark mica are typical. Common worldwide, especially in continental shields, mountain belts, and glacial deposits.
