igneous
Coarse-grained granite or granitic gneiss
Granite: quartz + feldspar + mica; possible gneissic equivalent
AI-generated identification · may be incorrectGray, white, and black interlocking crystals with a granular texture; vitreous quartz and feldspar, pearly-to-glassy mica. Typical hardness is about 6–7 Mohs, with no prominent cleavage as a whole and specific gravity around 2.6–2.8.
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Physical properties
Gray, white, and black interlocking crystals with a granular texture; vitreous quartz and feldspar, pearly-to-glassy mica. Typical hardness is about 6–7 Mohs, with no prominent cleavage as a whole and specific gravity around 2.6–2.8.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep underground, producing visible crystals; if the streaking is genuine foliation, it may have later undergone metamorphism into gneiss. Such rocks commonly formed during Precambrian to younger continental crust-building events.
Uses & applications
Used as building stone, countertops, monuments, aggregate, and decorative stone; attractive specimens may be collected, though this piece appears ordinary rather than gem-grade.
Geological facts
Granite is identified by visible quartz, feldspar, and dark mica or amphibole. Gneiss shows compositional banding or stretched mineral grains caused by intense heat and pressure.
Field identification & locations
Common worldwide, including the Sierra Nevada, Canadian Shield, Scandinavia, Brazil, and India. Look for hard interlocking grains, glassy gray quartz, pale feldspar, and black mica; a steel knife generally will not scratch quartz.
