igneous
Feldspar-rich granite or granitic pegmatite
Coarse-grained granite; primarily quartz (SiO₂), potassium feldspar/plagioclase, and minor biotite or amphibole
AI-generated identification · may be incorrectLight tan to gray, coarse interlocking crystals with a granular texture and vitreous to dull luster; Mohs hardness about 6–7, no consistent cleavage as a rock, and specific gravity roughly 2.6–2.7.
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Physical properties
Light tan to gray, coarse interlocking crystals with a granular texture and vitreous to dull luster; Mohs hardness about 6–7, no consistent cleavage as a rock, and specific gravity roughly 2.6–2.7.
Formation & geological history
Slow cooling of silica-rich magma deep within Earth produced the visible crystals, generally during Precambrian to Phanerozoic intrusive activity. The specimen may be weathered or broken from a larger plutonic body.
Uses & applications
Used as dimension stone, countertops, monuments, aggregate, and landscaping rock; attractive pieces are collected but usually have modest value.
Geological facts
Quartz appears glassy or gray, feldspar is commonly pink, cream, or white, and dark biotite forms black flakes. The coarse texture distinguishes it from volcanic rhyolite.
Field identification & locations
Common in continental crust and exposed in regions such as the Sierra Nevada, New England, Scandinavia, and many mountainous areas. A fresh broken surface showing interlocking quartz and feldspar supports identification.
