igneous
Coarse-grained granite or granitic gneiss
Granite (quartz–feldspar–mica aggregate), possibly weakly gneissic
AI-generated identification · may be incorrectMedium-coarse, speckled gray, cream, black, and pink grains; quartz and feldspar give a glassy to dull luster, while mica is platy. Hardness is about 6–7 Mohs, with no obvious cleavage as a whole and typical specific gravity of 2.63–2.75.
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Physical properties
Medium-coarse, speckled gray, cream, black, and pink grains; quartz and feldspar give a glassy to dull luster, while mica is platy. Hardness is about 6–7 Mohs, with no obvious cleavage as a whole and typical specific gravity of 2.63–2.75.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in continental crust, generally Precambrian to Phanerozoic in age; faint streaking could indicate later metamorphic deformation. Common in continental plutons and glacially transported gravel.
Uses & applications
Used widely as dimension stone, countertops, paving, monuments, aggregate, and landscaping material; attractive polished pieces have modest decorative value.
Geological facts
The visible interlocking crystals indicate slow cooling rather than volcanic eruption. Pink grains are potassium feldspar, pale translucent grains are quartz, and dark flakes are biotite or amphibole.
Field identification & locations
Identify it by its interlocking quartz–feldspar–dark-mineral texture and inability to scratch with a steel knife; acid testing should show no fizz. Exact identification requires a fresh surface, hand lens, and possibly thin-section analysis.
