Weathered granitic rock

Coarse-grained, speckled gray-tan rock with quartz, feldspar, and dark mica/amphibole; vitreous quartz luster, Mohs hardness about 6–7, no consistent cleavage as a whole, and typical specific gravity 2.63–2.75.

An intrusive igneous rock crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events; surface weathering has rounded and stained the specimen.

Used widely as dimension stone, countertops, monuments, aggregate, and landscape rock; attractive hand specimens generally sell for little unless unusually patterned or locality-labeled.

The granular texture records slow underground cooling, while rusty brown patches likely reflect oxidation of iron-bearing minerals. Exact identification would require a fresh surface or thin section.

Identify it by interlocking visible grains: translucent/gray quartz, pale feldspar, and black biotite or hornblende; it commonly occurs in continental shields, batholiths, and granitic gravel. A magnet, streak test, and close inspection of a fresh fracture can help distinguish it from gneiss or quartz-rich pegmatite.