igneous
Weathered granite or granitic gneiss
Granite; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, gray-white rock with dark mica/amphibole, granular texture, and uneven fracture; typical hardness is about 6–7 Mohs. The strongly weathered surface obscures the original crystalline structure, so exact identification from the image is uncertain.
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Physical properties
Coarse-grained, gray-white rock with dark mica/amphibole, granular texture, and uneven fracture; typical hardness is about 6–7 Mohs. The strongly weathered surface obscures the original crystalline structure, so exact identification from the image is uncertain.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic mountain-building events; surface weathering has altered this specimen. If foliated internally, it may instead be granitic gneiss, a metamorphic equivalent.
Uses & applications
Used extensively as dimension stone, countertops, monuments, crushed aggregate, and road material; unremarkable fragments have little commercial value.
Geological facts
Quartz commonly appears translucent gray, feldspar white or pink, and mica as black reflective flakes. Granite is identified by visible interlocking crystals rather than layers or rounded sedimentary grains.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts; test a fresh surface for quartz and feldspar, and compare with a streak, hardness, and acid test. Estimated value: $1–$10 for a common hand specimen, potentially $20–$75 if unusually attractive or locality-labeled.
