igneous
Weathered granite or granitic gneiss
Granite; primarily quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, mottled gray-brown specimen with visible pale feldspar/quartz and dark mica or altered minerals; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.8.
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Physical properties
Coarse-grained, mottled gray-brown specimen with visible pale feldspar/quartz and dark mica or altered minerals; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.8.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, typically during Precambrian–Phanerozoic intrusive events; surface weathering has likely produced the brown, rough exterior.
Uses & applications
Commonly used as dimension stone, countertops, monuments, aggregate, and building material; this small irregular fragment has little jewelry or commercial value.
Geological facts
Granite is an intrusive igneous rock, whereas granitic gneiss has similar minerals but foliation from metamorphism; the image is not detailed enough to distinguish them confidently.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts. Look for interlocking quartz and feldspar grains, scattered dark mica, and resistance to scratching by ordinary steel; a fresh broken surface would improve identification.
