igneous
Rounded granitic river pebble
Granite, chiefly quartz, feldspar, and mica; exact identification is uncertain from the image
AI-generated identification · may be incorrectLight gray, fine- to medium-grained, dull to weakly vitreous luster, with rounded weathered surfaces. Typical hardness is about 6–7 Mohs; massive texture, no obvious cleavage, and specific gravity around 2.6–2.7.
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Physical properties
Light gray, fine- to medium-grained, dull to weakly vitreous luster, with rounded weathered surfaces. Typical hardness is about 6–7 Mohs; massive texture, no obvious cleavage, and specific gravity around 2.6–2.7.
Formation & geological history
Crystallized slowly from silica-rich magma deep in the crust, likely hundreds of millions to billions of years ago; later erosion and transport rounded it in a stream, beach, or glacial deposit.
Uses & applications
Common granite is used for crushed aggregate, building stone, countertops, monuments, and landscaping; an ordinary pebble has little commercial value.
Geological facts
The pale grains likely represent quartz and feldspar, while darker specks may be biotite or other mafic minerals. Strong rounding indicates prolonged abrasion or transport.
Field identification & locations
Identify it by its interlocking granular texture, hardness, pale color, and resistance to scratching; quartz-rich granite typically scratches glass and does not fizz with dilute hydrochloric acid. Common worldwide, especially in granitic terrains and gravel deposits.
