igneous
Rounded granite or granitic gneiss cobble
Granite; predominantly quartz, feldspar, and minor biotite/amphibole
AI-generated identification · may be incorrectLight gray, fine-to-medium granular texture with scattered dark minerals and pinkish feldspar; nonmetallic luster, massive structure, no obvious cleavage as a whole, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.8.
Identified More igneous →
Explore Rounded granite or granitic gneiss cobble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Light gray, fine-to-medium granular texture with scattered dark minerals and pinkish feldspar; nonmetallic luster, massive structure, no obvious cleavage as a whole, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.8.
Formation & geological history
Crystallized slowly from silica-rich magma deep in the crust, likely hundreds of millions to billions of years ago, then exposed and rounded by weathering, stream transport, or glacial action. The image alone cannot distinguish granite confidently from closely related granitic gneiss.
Uses & applications
Commonly used as crushed aggregate, road stone, landscape stone, countertops, and building material; this rounded specimen has little commercial value but may be useful as a decorative or teaching sample.
Geological facts
The rounded shape is transport-worn rather than its original crystalline form. Small dark grains are likely biotite or amphibole, while pink areas are potassium feldspar.
Field identification & locations
Look for visible interlocking quartz and feldspar grains, a hard scratch-resistant surface, and a speckled appearance; acid produces no reaction. Common in granitic terrains worldwide, especially streambeds and glacial deposits.
