igneous
Dark gray granite (probable)
Granite; mainly quartz (SiO₂), feldspar, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, speckled gray-black rock with granular texture and likely interlocking crystals; hardness about 6–7 Mohs, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
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Physical properties
Coarse-grained, speckled gray-black rock with granular texture and likely interlocking crystals; hardness about 6–7 Mohs, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity roughly 2.6–2.8.
Formation & geological history
Granite forms when silica-rich magma cools slowly deep within continental crust, allowing large crystals to grow; specimens may range from Precambrian to younger Phanerozoic ages.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and construction material; small natural pieces have minimal commercial value.
Geological facts
The dark grains are likely biotite mica, hornblende, or weathered mafic minerals, while lighter grains are feldspar and quartz. Exact identification requires a fresh surface or hand-lens examination.
Field identification & locations
Common worldwide in continental mountain belts and exposed plutons. Identify it by visible interlocking quartz/feldspar crystals and a lack of layering or foliation; it could also be a related diorite if quartz is scarce.
