igneous
Weathered granite or granitic gneiss
Granite; primarily quartz (SiO₂), feldspar, and mica, possibly with metamorphic foliation
AI-generated identification · may be incorrectCoarse-grained, gray to brown, with a granular crystalline texture and dull to faintly vitreous luster; typical Mohs hardness is about 6–7, with no prominent cleavage as a whole rock. The image suggests weathered feldspar and dark mica or amphibole.
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Physical properties
Coarse-grained, gray to brown, with a granular crystalline texture and dull to faintly vitreous luster; typical Mohs hardness is about 6–7, with no prominent cleavage as a whole rock. The image suggests weathered feldspar and dark mica or amphibole.
Formation & geological history
Likely formed by slow cooling of silica-rich magma deep in the continental crust, generally during Precambrian to younger plutonic events; surface weathering has altered its minerals and produced the brown coloration.
Uses & applications
Common granite is used as crushed aggregate, building stone, countertops, monuments, and landscaping material; an ordinary hand specimen has little commercial value.
Geological facts
Quartz appears glassy gray, feldspar is white or tan, and biotite or amphibole forms dark grains. A definitive identification would require a fresh surface, hand lens, and tests for quartz and feldspar.
Field identification & locations
Common in continental mountain belts and exposed shields worldwide, including North America, Europe, Africa, and Australia. Look for interlocking visible grains; streak, acid, and hardness tests can help distinguish it from sandstone or concrete.
