igneous
Likely weathered granite or granitic pegmatite fragment
Granite, composed mainly of quartz, feldspar, and dark mica or amphibole
AI-generated identification · may be incorrectCoarse-grained, mottled brown, cream, gray, and black; likely Mohs 6–7, with vitreous quartz and feldspar luster. Crystals are interlocking and lack obvious cleavage as a whole, though feldspar shows cleavage.
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Physical properties
Coarse-grained, mottled brown, cream, gray, and black; likely Mohs 6–7, with vitreous quartz and feldspar luster. Crystals are interlocking and lack obvious cleavage as a whole, though feldspar shows cleavage.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma deep underground, generally during Precambrian to Phanerozoic continental-crust formation; surface weathering produced the brown staining.
Uses & applications
Used widely as dimension stone, countertops, paving, monuments, and aggregate; ordinary fragments have little jewelry or collector value.
Geological facts
The image appears to show a rough, weathered fragment rather than a complete diagnostic specimen, and the adjacent dark pieces may be unrelated rocks.
Field identification & locations
Look for visible quartz, pale feldspar, and black mica in a coarse interlocking texture; a streak test is unhelpful, while a steel file generally does not scratch fresh quartz. Common worldwide, especially in continental shields and mountain batholiths.
