igneous
Rounded gray granitoid pebble
Granite or granodiorite; chiefly quartz, feldspar, and mica/hornblende
AI-generated identification · may be incorrectMedium- to coarse-grained, gray with white mineral patches and dark specks; vitreous to dull luster, interlocking crystalline texture, Mohs hardness about 6–7, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
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Physical properties
Medium- to coarse-grained, gray with white mineral patches and dark specks; vitreous to dull luster, interlocking crystalline texture, Mohs hardness about 6–7, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
Formation & geological history
Crystallized slowly from silica-rich magma deep in continental crust, then exposed and rounded by weathering, streams, or glacial transport; its exact geological age cannot be determined from the image.
Uses & applications
Used extensively as dimension stone, countertops, monuments, aggregate, and decorative landscaping rock; small rounded pieces have modest collecting appeal.
Geological facts
Granite is an intrusive igneous rock, while granodiorite contains relatively more plagioclase than potassium feldspar and is often slightly darker.
Field identification & locations
Identify it by visible interlocking quartz and feldspar grains, gray-pink coloration, and hardness sufficient to scratch glass; common worldwide, especially in continental mountain belts and glacial deposits.
