igneous
Rounded granite pebble
Granite, chiefly quartz, feldspar, and mica; approximate composition SiO₂-rich felsic rock
AI-generated identification · may be incorrectCoarse crystalline, pale pink-gray, with white/cream feldspar, translucent quartz, and dark biotite or hornblende. Hardness is about 6–7 Mohs; generally non-cleavable as a rock, with vitreous quartz and pearly feldspar luster; specific gravity about 2.6–2.7.
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Physical properties
Coarse crystalline, pale pink-gray, with white/cream feldspar, translucent quartz, and dark biotite or hornblende. Hardness is about 6–7 Mohs; generally non-cleavable as a rock, with vitreous quartz and pearly feldspar luster; specific gravity about 2.6–2.7.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic plutonic events. The specimen’s smooth shape likely results from stream or beach abrasion and weathering.
Uses & applications
Used extensively as dimension stone, countertops, monuments, paving, aggregate, and building stone; attractive polished pieces are collected but are usually low-value.
Geological facts
The mottled texture reflects interlocking crystals that cooled over thousands to millions of years. Pink coloration commonly comes from potassium feldspar, while dark flecks are mafic minerals.
Field identification & locations
Identify it by visible interlocking quartz and feldspar crystals, pink-gray coloration, and lack of layering or foliation; a streak, acid, and hardness test can help distinguish it from quartzite or weathered gneiss. Common worldwide, especially in continental shields and mountain batholiths.
