igneous
Rounded granite pebble
Granite, chiefly quartz, potassium feldspar, and plagioclase with minor mica or amphibole
AI-generated identification · may be incorrectFine- to medium-grained, gray and speckled, with a dull to slightly granular luster; hardness about 6–7 Mohs, massive structure, no cleavage as a whole, and typical specific gravity 2.6–2.7.
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Physical properties
Fine- to medium-grained, gray and speckled, with a dull to slightly granular luster; hardness about 6–7 Mohs, massive structure, no cleavage as a whole, and typical specific gravity 2.6–2.7.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma, commonly millions to billions of years ago; its rounded shape reflects river, beach, or glacial abrasion.
Uses & applications
Used as aggregate, paving stone, building stone, countertops, and landscaping material; this small specimen has minimal commercial value.
Geological facts
The interlocking grains indicate slow underground cooling. Individual quartz grains should scratch glass, while feldspar commonly shows flat cleavage surfaces.
Field identification & locations
Common worldwide, especially in continental shields and mountain ranges. Identify it by its coarse interlocking gray, white, and black grains, lack of layering, and inability to fizz with dilute acid; exact identification is limited by the small image.
