igneous
Coarse-grained granite
Granite; predominantly quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; speckled white, gray, black, and pink, with a crystalline granular texture and generally nonfoliated structure. It has a vitreous quartz luster, feldspar cleavage, and specific gravity around 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; speckled white, gray, black, and pink, with a crystalline granular texture and generally nonfoliated structure. It has a vitreous quartz luster, feldspar cleavage, and specific gravity around 2.6–2.7.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly deep underground, allowing large crystals to develop; its exact age cannot be determined from the image and may range from Precambrian to geologically recent.
Uses & applications
Used widely as dimension stone, countertops, paving, monuments, aggregate, and building stone; attractive polished pieces have modest decorative or lapidary value.
Geological facts
The visible interlocking crystals and lack of layering distinguish granite from sedimentary and foliated metamorphic rocks. Dark grains are likely biotite or hornblende, while translucent grains are quartz.
Field identification & locations
Common worldwide, including India, Brazil, Scandinavia, Canada, and the United States; identify it by coarse interlocking quartz and feldspar crystals, unlike concrete, which contains rounded aggregate in a cement matrix.
