igneous
Weathered granitic pebble
Granite, likely quartz–feldspar–biotite aggregate
AI-generated identification · may be incorrectCoarse-grained, mottled gray-brown and tan with visible pale feldspar/quartz and dark mica or mafic grains; typically Mohs 6–7, vitreous to dull luster, interlocking crystals, no cleavage as a whole, and specific gravity about 2.6–2.7.
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Physical properties
Coarse-grained, mottled gray-brown and tan with visible pale feldspar/quartz and dark mica or mafic grains; typically Mohs 6–7, vitreous to dull luster, interlocking crystals, no cleavage as a whole, and specific gravity about 2.6–2.7.
Formation & geological history
Intrusive igneous rock formed by slow cooling of silica-rich magma, generally within continental crust during Precambrian to Mesozoic or younger plutonic events; this pebble was rounded by weathering and transport.
Uses & applications
Used as crushed aggregate, building stone, curbing, and decorative landscaping material; this small weathered fragment has negligible commercial value.
Geological facts
Granite is a rock rather than a single mineral, commonly dominated by quartz, potassium feldspar, plagioclase, and mica. Brown coloration may result from iron-oxide weathering of biotite or feldspar.
Field identification & locations
Identify it by its speckled, interlocking crystals and resistance to scratching; quartz and feldspar grains are usually visible, unlike fine-grained basalt. Common in glacial deposits, stream gravels, and areas surrounding granitic plutons.
