igneous
Rounded granite pebble
Granite, chiefly quartz, potassium feldspar, plagioclase, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, speckled gray-green surface with a granular texture and weak vitreous luster; typical hardness is about 6–7 Mohs, with no obvious cleavage as a whole rock and specific gravity around 2.6–2.7.
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Physical properties
Coarse-grained, speckled gray-green surface with a granular texture and weak vitreous luster; typical hardness is about 6–7 Mohs, with no obvious cleavage as a whole rock and specific gravity around 2.6–2.7.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma deep in Earth’s crust, generally during Precambrian to Phanerozoic plutonic events. Its rounded shape and smoothed surface result from transport and abrasion on a beach or in a gravel deposit.
Uses & applications
Used extensively as building stone, countertops, monuments, paving, aggregate, and decorative landscaping material; this small waterworn piece is mainly a beach or collection specimen.
Geological facts
Individual mineral grains are visible because slow cooling allowed large crystals to form. A fresh surface commonly reacts weakly or not at all with dilute hydrochloric acid, unlike limestone.
Field identification & locations
Identify it by interlocking visible grains of light quartz/feldspar and darker minerals, lack of layering, and a very hard, abrasion-resistant surface; a streak or fresh fracture helps confirm it. Common worldwide in continental crust and glacial, river, and coastal gravels.
