igneous
Gray granite or granitic gneiss gravel
Granite; primarily quartz, feldspar, and mica (exact identification is uncertain from the photograph)
AI-generated identification · may be incorrectCoarse-grained, gray, and nonmetallic with a granular texture; typical hardness is about 6–7 Mohs, with uneven fracture and variable density around 2.6–2.8 g/cm³. The specimen appears weathered and may show weak foliation, suggesting gneiss rather than granite.
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Physical properties
Coarse-grained, gray, and nonmetallic with a granular texture; typical hardness is about 6–7 Mohs, with uneven fracture and variable density around 2.6–2.8 g/cm³. The specimen appears weathered and may show weak foliation, suggesting gneiss rather than granite.
Formation & geological history
Formed by slow cooling of silica-rich magma deep underground; if gneissic, it was later altered by intense heat and pressure. Such rocks commonly range from Precambrian to younger continental-crust ages.
Uses & applications
Commonly crushed for roads, railway ballast, drainage, landscaping, and aggregate; attractive polished granite is used for countertops and monuments. This ordinary gravel piece has little jewelry or collector value.
Geological facts
Granite is one of Earth’s most abundant continental rocks and commonly contains visibly contrasting light feldspar, translucent quartz, and dark biotite or hornblende.
Field identification & locations
Identify it by its interlocking grains and mixed light-gray, white, and dark minerals; a streak test is usually white, and acid produces no reaction. Common in continental mountain belts and glacial or quarry-derived gravel deposits.
