igneous
Polished granite pebble
Granite; chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; coarse, mottled gray, white, pink, and dark green-black appearance with a vitreous to dull luster. Interlocking crystalline texture and no prominent cleavage as a whole; feldspar crystals may show cleavage.
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Physical properties
Hardness about 6–7 Mohs; coarse, mottled gray, white, pink, and dark green-black appearance with a vitreous to dull luster. Interlocking crystalline texture and no prominent cleavage as a whole; feldspar crystals may show cleavage.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma, commonly millions to billions of years ago, then rounded by stream or beach erosion and naturally or artificially polished.
Uses & applications
Used widely as building stone, countertops, monuments, aggregate, landscaping material, and decorative polished specimens. This small pebble has modest collector value.
Geological facts
The pale grains are likely quartz and feldspar, while dark grains may be biotite, hornblende, or altered minerals. Rusty patches commonly reflect oxidation of iron-bearing minerals.
Field identification & locations
Identify it by its visibly interlocking grains, mixed light and dark minerals, lack of layering, and inability to scratch easily with a steel knife. Common worldwide, especially in exposed continental mountain belts and glacial or river deposits.
