igneous
Granite or granitic gneiss pebble
Quartz–feldspar–mica aggregate; likely weathered granite, possibly weakly gneissic
AI-generated identification · may be incorrectCoarse, speckled gray-brown rock with translucent quartz, pale feldspar, and dark biotite/hornblende; typically Mohs 6–7, granular texture, vitreous-to-dull luster, no obvious cleavage as a whole, and specific gravity about 2.6–2.8.
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Physical properties
Coarse, speckled gray-brown rock with translucent quartz, pale feldspar, and dark biotite/hornblende; typically Mohs 6–7, granular texture, vitreous-to-dull luster, no obvious cleavage as a whole, and specific gravity about 2.6–2.8.
Formation & geological history
Formed when silica-rich magma crystallized slowly deep underground, commonly during Precambrian to Phanerozoic continental crust formation; surface rounding indicates erosion and transport as a pebble or cobble.
Uses & applications
Used as crushed aggregate, building stone, paving, landscaping material, and occasional polished decorative stone; this rounded specimen has modest collector value.
Geological facts
Granite’s visible interlocking crystals record slow cooling, while orange-brown areas likely reflect iron-oxide staining or weathered feldspar.
Field identification & locations
Identify it by its randomly interlocking quartz, feldspar, and dark mica grains; it is common in continental mountain belts and glacial or river gravels worldwide. A streak test, hand lens, and acid test can help distinguish it from basalt or sandstone.
