igneous
Black-and-white granite
Granite, chiefly quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectCoarse-grained, phaneritic texture with white to gray feldspar/quartz and black biotite or hornblende; vitreous quartz and variable feldspar luster. Mohs hardness is approximately 6–7; no consistent cleavage as a rock, though feldspar crystals cleave; specific gravity about 2.63–2.75.
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Physical properties
Coarse-grained, phaneritic texture with white to gray feldspar/quartz and black biotite or hornblende; vitreous quartz and variable feldspar luster. Mohs hardness is approximately 6–7; no consistent cleavage as a rock, though feldspar crystals cleave; specific gravity about 2.63–2.75.
Formation & geological history
An intrusive felsic igneous rock formed by slow crystallization of silica-rich magma deep in Earth’s crust, commonly during Precambrian to younger continental mountain-building events. The rounded shape indicates tumbling or natural abrasion.
Uses & applications
Used as dimension stone, countertops, monuments, aggregate, landscaping stone, and inexpensive polished specimens. This small piece has little jewelry value unless it displays unusually attractive crystals or provenance.
Geological facts
Its salt-and-pepper appearance results from interlocking light feldspar/quartz and dark mafic minerals. Granite commonly weathers to sandy grus and supports many continental mountain ranges.
Field identification & locations
Identify it by visible interlocking crystals, hardness, and the absence of vesicles or layering; a streak test is generally white. Common worldwide, especially in continental shields and batholiths; likely sources cannot be determined from the image alone.
