igneous
Granite (weathered, possibly granitic gneiss)
Granite; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectLight gray to tan, coarse crystalline texture with faint dark mica; typically vitreous to dull luster, no cleavage as a rock, Mohs hardness about 6–7, and specific gravity 2.63–2.75. The image’s weathering obscures individual grains, so gneiss is a possible alternative if banding is present.
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Physical properties
Light gray to tan, coarse crystalline texture with faint dark mica; typically vitreous to dull luster, no cleavage as a rock, Mohs hardness about 6–7, and specific gravity 2.63–2.75. The image’s weathering obscures individual grains, so gneiss is a possible alternative if banding is present.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building events; exposed surfaces weather to rounded boulders and granular debris.
Uses & applications
Widely used as dimension stone, countertops, paving, monuments, building aggregate, and landscaping rock; generally low collector value as an ordinary boulder.
Geological facts
Quartz commonly appears translucent gray, feldspar white or pink, and biotite black. Rounded, exfoliated surfaces and sandy granitic grit indicate prolonged chemical and physical weathering.
Field identification & locations
Identify it by interlocking visible quartz and feldspar grains, scattered mica, lack of layering, and inability to scratch with a steel knife; fizzing with dilute acid is not expected. Common worldwide in continental crust and glaciated landscapes.
