igneous
Rounded granite pebble
Granite; primarily quartz, potassium feldspar, plagioclase, and minor biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pinkish-tan, fine- to medium-grained, granular texture, and dull to weakly vitreous luster. Interlocking crystals are visible as speckles; cleavage occurs in feldspar, but the pebble has no overall cleavage.
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Physical properties
Hardness about 6–7 Mohs; pinkish-tan, fine- to medium-grained, granular texture, and dull to weakly vitreous luster. Interlocking crystals are visible as speckles; cleavage occurs in feldspar, but the pebble has no overall cleavage.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic intrusive events. Its rounded shape and smooth surface result from transport and abrasion in a river, beach, or glacial environment.
Uses & applications
Used extensively as dimension stone, paving, aggregate, countertops, monuments, and landscaping rock. A single rounded pebble generally has little commercial value but may be useful for teaching or collecting.
Geological facts
The pink coloration most likely comes from potassium feldspar, while darker flecks may be biotite or amphibole. Weathering can produce the tan, slightly softened surface visible here.
Field identification & locations
Identify it by its hard, speckled, interlocking crystalline texture and inability to be scratched easily with a steel knife; glassy quartz grains and pink feldspar are diagnostic. Common worldwide in granitic terrains and stream or beach gravels.
