igneous
Granite pebble
Coarse-grained granitic rock, primarily quartz–feldspar–biotite
AI-generated identification · may be incorrectTypically 6–7 Mohs; pink, white, gray, and black granular appearance; vitreous quartz and dull-to-pearly feldspar, with no foliation and irregular fracture. Visible interlocking crystals indicate a phaneritic texture; specific gravity is about 2.6–2.7.
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Physical properties
Typically 6–7 Mohs; pink, white, gray, and black granular appearance; vitreous quartz and dull-to-pearly feldspar, with no foliation and irregular fracture. Visible interlocking crystals indicate a phaneritic texture; specific gravity is about 2.6–2.7.
Formation & geological history
Forms when silica-rich magma cools slowly deep within continental crust, allowing large crystals to grow; most granite bodies are Precambrian to Mesozoic, though the pebble itself was later weathered and transported.
Uses & applications
Used widely as crushed stone, aggregate, dimension stone, countertops, monuments, and decorative landscaping material; ordinary pebbles have little commercial value.
Geological facts
The black grains are likely biotite or hornblende, while pink areas are potassium feldspar and pale translucent grains are quartz. The rounded shape reflects abrasion during stream or beach transport.
Field identification & locations
Identify it by its coarse, interlocking quartz–feldspar texture, mixed pink/gray/black color, and lack of layering or strong foliation; common worldwide, especially in granitic terrains and river gravels.
