igneous
Weathered granite or granitic gneiss
Granite; mainly quartz (SiO₂), feldspar, and mica, possibly with metamorphic foliation
AI-generated identification · may be incorrectCoarse-grained, speckled gray, cream, and black material with a granular texture and dull to slightly vitreous luster. Hardness is about 6–7 Mohs; quartz and feldspar show no obvious cleavage in the fragment, while mica may split into flakes.
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Physical properties
Coarse-grained, speckled gray, cream, and black material with a granular texture and dull to slightly vitreous luster. Hardness is about 6–7 Mohs; quartz and feldspar show no obvious cleavage in the fragment, while mica may split into flakes.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep within Earth, generally during Precambrian to Phanerozoic continental crust formation; if foliated, it may have been metamorphosed into gneiss. Weathering has roughened and stained the surface.
Uses & applications
Commonly used as crushed aggregate, building stone, countertops, monuments, and decorative material; this small weathered fragment has little jewelry use.
Geological facts
Granite is identified by visible interlocking crystals rather than layers or cemented grains. Dark flecks are likely biotite or hornblende, while pale grains are feldspar and translucent grains may be quartz.
Field identification & locations
Look for randomly interlocking light and dark grains, high hardness, and resistance to scratching; a steel knife usually struggles to scratch it. Common worldwide in continental shields, mountain ranges, and exposed plutons.
