igneous
Weathered granite or granitic gneiss pebble
Granite; chiefly quartz (SiO₂), feldspar, and mica; possibly weakly gneissic
AI-generated identification · may be incorrectCoarse, mottled gray-tan rock with pale feldspar, translucent quartz, dark mica, and a reddish weathered zone; uneven granular texture, no obvious cleavage, Mohs hardness about 6–7, vitreous to dull luster, and specific gravity roughly 2.6–2.8.
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Physical properties
Coarse, mottled gray-tan rock with pale feldspar, translucent quartz, dark mica, and a reddish weathered zone; uneven granular texture, no obvious cleavage, Mohs hardness about 6–7, vitreous to dull luster, and specific gravity roughly 2.6–2.8.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to younger continental events; gneissic banding would reflect later high-grade metamorphism. The rounded shape indicates prolonged stream or beach abrasion and weathering.
Uses & applications
Common granite is used as crushed aggregate, dimension stone, monuments, countertops, and landscaping material; ordinary pebbles have little jewelry value.
Geological facts
Quartz resists weathering while feldspar alters to clay, producing the pale, softened surface visible here. The image does not show diagnostic crystal size or foliation clearly enough for a precise rock name.
Field identification & locations
Look for interlocking visible quartz and feldspar grains, scattered dark mica, and a hard, nonporous surface; a streak test is usually white, and dilute acid should not fizz. Common worldwide in granitic terrains, riverbeds, and glacial deposits.
