igneous
Granite pebble
Granite, typically quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectCoarse-grained, speckled gray rock with abundant reflective mica; likely hardness 6–7 Mohs, vitreous to pearly luster, interlocking crystals, no cleavage as a rock, and specific gravity about 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray rock with abundant reflective mica; likely hardness 6–7 Mohs, vitreous to pearly luster, interlocking crystals, no cleavage as a rock, and specific gravity about 2.63–2.75.
Formation & geological history
Intrusive igneous rock crystallized slowly from silica-rich magma deep in Earth’s crust, commonly during Precambrian to Phanerozoic mountain-building; its rounded shape indicates transport by water, ice, or weathering.
Uses & applications
Used extensively for building stone, countertops, monuments, aggregate, and landscaping; attractive polished pieces are collected but usually have modest value.
Geological facts
The bright sparkles are probably muscovite or biotite mica, while pale grains are feldspar and translucent grains may be quartz.
Field identification & locations
Identify it by its visible interlocking grains, salt-and-pepper texture, and lack of layering or foliation; common worldwide in continental crust and glacial or river gravels. A hand lens and scratch test help distinguish it from similar gneiss or diorite.
