igneous
Weathered granite boulder
Granite, a coarse-grained felsic intrusive igneous rock composed chiefly of quartz, potassium feldspar, plagioclase, and biotite or other micas
AI-generated identification · may be incorrectTypically Mohs 6–7; gray to pinkish-brown, with visible interlocking grains and a granular texture. It has a vitreous quartz/feldspar luster, no preferred cleavage as a rock, and specific gravity around 2.6–2.7; the surface is heavily weathered and lichen-stained.
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Physical properties
Typically Mohs 6–7; gray to pinkish-brown, with visible interlocking grains and a granular texture. It has a vitreous quartz/feldspar luster, no preferred cleavage as a rock, and specific gravity around 2.6–2.7; the surface is heavily weathered and lichen-stained.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, commonly during Precambrian to Mesozoic mountain-building events. Uplift, erosion, and weathering exposed the boulder.
Uses & applications
Used extensively as dimension stone, building aggregate, curbing, monuments, countertops, and landscaping rock. This weathered specimen has little gem or collector value.
Geological facts
Granite’s large crystals record slow underground cooling; rounded boulders commonly develop through spheroidal weathering and transport. Orange-brown patches likely represent iron-oxide staining or weathered biotite.
Field identification & locations
Identify it by its visible quartz and feldspar grains, hard granular texture, and lack of layering or foliation; it commonly occurs in continental plutons, mountain belts, glacial deposits, and stream gravels. A hand lens and streak/acid tests can help distinguish it from similar granitic rocks.
