igneous
Weathered granite or granitic gneiss pebble
Granite; chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; coarse, granular texture with pale feldspar/quartz and rusty iron-oxide staining. Typically vitreous to dull luster, no consistent cleavage as a whole, and specific gravity around 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; coarse, granular texture with pale feldspar/quartz and rusty iron-oxide staining. Typically vitreous to dull luster, no consistent cleavage as a whole, and specific gravity around 2.6–2.7.
Formation & geological history
Crystallized slowly from silica-rich magma deep within the continental crust, generally during Precambrian to younger mountain-building events; the rounded shape reflects erosion and transport. The orange-brown surface comes from weathering of iron-bearing minerals.
Uses & applications
Commonly used as crushed stone, aggregate, paving, and dimension stone; attractive pieces may be used as landscape or teaching specimens. This ordinary pebble has little jewelry value.
Geological facts
Granite is an intrusive igneous rock, while gneiss has similar minerals but visible compositional banding from metamorphism; the image does not show enough detail for a certain distinction.
Field identification & locations
Look for interlocking visible grains of glassy quartz and white/pink feldspar, often with dark mica or amphibole; a streak, acid, and fresh broken surface help confirm it. Common in glacial deposits, stream gravels, and eroded mountain regions.
