igneous
Gray granite or granitic gneiss
Granite; typically quartz + feldspar + mica (approx. SiO₂-rich granitoid)
AI-generated identification · may be incorrectCoarse-grained, light-to-medium gray, speckled white and dark minerals, with a granular crystalline texture and uneven fracture; hardness about 6–7 Mohs and specific gravity roughly 2.6–2.8. The foliation-like streaking could indicate weakly banded gneiss rather than true granite.
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Physical properties
Coarse-grained, light-to-medium gray, speckled white and dark minerals, with a granular crystalline texture and uneven fracture; hardness about 6–7 Mohs and specific gravity roughly 2.6–2.8. The foliation-like streaking could indicate weakly banded gneiss rather than true granite.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to younger continental mountain-building events; gneiss forms when granite is subjected to intense metamorphic heat and pressure. The specimen appears naturally weathered and possibly quarried or landscaping-grade.
Uses & applications
Widely used as crushed aggregate, road stone, building stone, monuments, countertops, and paving; attractive polished pieces may be used decoratively. This rough fragment has little jewelry value.
Geological facts
Visible light quartz/feldspar and darker biotite or amphibole produce the characteristic salt-and-pepper appearance. Granite is one of Earth’s most abundant continental crust rocks.
Field identification & locations
Identify it by visible interlocking grains, abundant pale feldspar/quartz, and scattered black mica or amphibole; it will not fizz with dilute acid. Common worldwide in continental shields, mountain belts, and quarries.
