igneous
Granite or granitic gneiss pebble
Quartz–feldspar–mica aggregate; likely granite, possibly foliated gneiss
AI-generated identification · may be incorrectCoarse-grained, gray and white, with dark mica or amphibole; granular texture, vitreous quartz, and no obvious cleavage. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
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Physical properties
Coarse-grained, gray and white, with dark mica or amphibole; granular texture, vitreous quartz, and no obvious cleavage. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust; gneiss forms when granite is intensely metamorphosed. Such material is generally Precambrian to younger and commonly released as stream or glacial cobbles.
Uses & applications
Used as crushed stone, dimension stone, countertops, monuments, and landscape rock; this small rounded specimen is mainly suitable for collecting.
Geological facts
The pale grains are likely feldspar and quartz, while darker grains are biotite mica or hornblende. Rounded edges indicate transport and weathering rather than original crystal shape.
Field identification & locations
Identify it by its visible interlocking grains, mixed white-gray-black color, and lack of sedimentary layering; a streak test is ineffective. Common in continental crust, mountain belts, glacial deposits, and river gravels.
