igneous
Weathered quartz-rich rock fragment
Likely quartz–feldspar-rich granitoid, possibly granite or granitic gneiss; exact identification is uncertain from the image
AI-generated identification · may be incorrectGray, cream, and rusty-brown mottling with a rough, granular surface and no obvious cleavage; likely quartz and feldspar with iron-oxide staining. Quartz has Mohs hardness 7; whole-rock hardness varies with composition.
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Physical properties
Gray, cream, and rusty-brown mottling with a rough, granular surface and no obvious cleavage; likely quartz and feldspar with iron-oxide staining. Quartz has Mohs hardness 7; whole-rock hardness varies with composition.
Formation & geological history
Likely formed when silica-rich magma cooled slowly underground, or from metamorphism of similar rock; its age and precise origin cannot be determined visually. Weathering and transport rounded the surrounding gravel.
Uses & applications
Common granitoid is used as crushed aggregate, building and paving stone, and sometimes decorative stone; this small fragment has little commercial value.
Geological facts
Rusty colors commonly result when iron-bearing minerals oxidize during weathering.
Field identification & locations
Look for interlocking visible grains of quartz and feldspar; a fresh broken surface and a hand lens would help distinguish granite from gneiss or other rocks. Granitoids occur widely in continental crust and river or beach gravels.
