igneous
Weathered granitic rock
Granite or granodiorite; chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, mottled pink, white, gray, and brown with visible interlocking crystals; quartz has Mohs hardness 7, feldspar 6–6.5, and the overall rock is typically nonfoliated with weak cleavage inherited from feldspar. The rusty brown areas likely reflect iron-oxide weathering.
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Physical properties
Coarse-grained, mottled pink, white, gray, and brown with visible interlocking crystals; quartz has Mohs hardness 7, feldspar 6–6.5, and the overall rock is typically nonfoliated with weak cleavage inherited from feldspar. The rusty brown areas likely reflect iron-oxide weathering.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma several kilometers underground, commonly during Precambrian to Phanerozoic mountain-building events; surface weathering produced the brown staining.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving aggregate, and crushed stone; attractive hand specimens have modest collecting value.
Geological facts
Granite’s interlocking crystals form because magma cools slowly, unlike volcanic rhyolite, which is fine-grained. Pink coloration usually comes from potassium feldspar.
Field identification & locations
Identify it by visible quartz and feldspar crystals, granular texture, and lack of layering or foliation; common worldwide in continental crust, including Canada, the United States, Brazil, India, and Scandinavia. A fresh broken surface and hardness test help distinguish it from sandstone or gneiss.
