igneous
Weathered granite cobble
Granite, typically quartz–feldspar–mica assemblage
AI-generated identification · may be incorrectCoarse, speckled texture with pale feldspar/quartz and dark biotite or hornblende; Mohs hardness about 6–7, vitreous to dull luster, massive structure, and no cleavage as a whole rock. The brown-orange surface is likely iron-oxide weathering.
Identified More igneous →
Explore Weathered granite cobble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, speckled texture with pale feldspar/quartz and dark biotite or hornblende; Mohs hardness about 6–7, vitreous to dull luster, massive structure, and no cleavage as a whole rock. The brown-orange surface is likely iron-oxide weathering.
Formation & geological history
Intrusive igneous rock crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events; later erosion and weathering rounded it into a cobble.
Uses & applications
Used as crushed aggregate, building stone, paving, monuments, and landscaping rock; attractive polished pieces may be used decoratively but this specimen has limited gemstone value.
Geological facts
Granite’s visible crystals indicate slow underground cooling. Its rounded shape and weathered rind suggest transport by a river, beach, or glacial system.
Field identification & locations
Identify by interlocking visible quartz and feldspar grains, dark mica/hornblende, high hardness, and lack of layering or vesicles; common worldwide in continental mountain belts and granite terrains.
