igneous
Weathered granite pebble
Granite, mainly quartz, feldspar, and mica; approximate composition SiO₂-rich continental crust
AI-generated identification · may be incorrectCoarse-grained, speckled cream-gray rock with dark biotite/hornblende and rusty iron-oxide staining; quartz and feldspar have Mohs hardness about 6–7, with no prominent cleavage in the overall rock. Typically has a granular texture and moderate-to-high density (~2.6–2.7 g/cm³).
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Physical properties
Coarse-grained, speckled cream-gray rock with dark biotite/hornblende and rusty iron-oxide staining; quartz and feldspar have Mohs hardness about 6–7, with no prominent cleavage in the overall rock. Typically has a granular texture and moderate-to-high density (~2.6–2.7 g/cm³).
Formation & geological history
Formed when silica-rich magma slowly crystallized deep underground, generally during Precambrian to Phanerozoic continental geological events; the rounded shape indicates abrasion in a stream, beach, or glacial environment.
Uses & applications
Used as aggregate, building stone, monuments, countertops, and landscaping material; this ordinary rounded specimen has little jewelry value.
Geological facts
Granite’s visible crystals record slow cooling beneath Earth’s surface. The orange-brown areas are likely weathering products of iron-bearing minerals.
Field identification & locations
Identify it by its interlocking visible grains, pale quartz/feldspar, and scattered dark mica or amphibole; unlike sandstone, it lacks cemented sedimentary layers. Common worldwide, especially in continental shield and mountain regions.
