igneous
Granite
Granite, predominantly quartz–feldspar–mica rock
AI-generated identification · may be incorrectCoarse-grained, speckled white, gray, tan, and dark brown; quartz has Mohs hardness 7, feldspar 6–6.5, and mica 2–3. Typically vitreous quartz luster, interlocking crystals, and no cleavage as a whole, though feldspar and mica show cleavage; specific gravity about 2.63–2.75.
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Physical properties
Coarse-grained, speckled white, gray, tan, and dark brown; quartz has Mohs hardness 7, feldspar 6–6.5, and mica 2–3. Typically vitreous quartz luster, interlocking crystals, and no cleavage as a whole, though feldspar and mica show cleavage; specific gravity about 2.63–2.75.
Formation & geological history
A plutonic igneous rock formed by slow cooling and crystallization of silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Widely used for countertops, monuments, building stone, aggregate, and paving; attractive hand specimens are collected, though this small piece usually has modest value.
Geological facts
Its visible interlocking crystals indicate slow underground cooling. The dark flakes are likely biotite mica, while white or pink grains are feldspar and translucent grains may be quartz.
Field identification & locations
Identify it by coarse interlocking grains, abundant light-colored feldspar/quartz, and scattered dark mica; it commonly occurs in continental plutons, mountain cores, and glacial deposits worldwide. A hand lens and scratch test help distinguish it from fine-grained rocks.
