igneous
Rounded granite pebble
Granite, chiefly quartz, alkali feldspar, plagioclase feldspar, and biotite/hornblende
AI-generated identification · may be incorrectMedium- to coarse-grained, pink, white, gray, and black speckled appearance; granular texture and vitreous to dull luster. Mohs hardness is about 6–7; crystals are interlocking with no prominent cleavage as a whole, and specific gravity is approximately 2.63–2.75.
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Physical properties
Medium- to coarse-grained, pink, white, gray, and black speckled appearance; granular texture and vitreous to dull luster. Mohs hardness is about 6–7; crystals are interlocking with no prominent cleavage as a whole, and specific gravity is approximately 2.63–2.75.
Formation & geological history
An intrusive felsic igneous rock crystallized slowly from magma deep in the continental crust, commonly during Precambrian to Phanerozoic mountain-building events. Its rounded shape indicates abrasion by water, ice, or transport as a tumbled specimen.
Uses & applications
Used extensively as dimension stone, countertops, paving, monuments, aggregate, and landscaping rock; attractive polished pieces are collected but usually have modest value.
Geological facts
Pink coloration generally reflects potassium feldspar, while black grains are biotite or amphibole and translucent grains are quartz. Granite’s coarse crystals record slow underground cooling.
Field identification & locations
Identify it by visible interlocking pink feldspar, gray/clear quartz, and black mica or amphibole; it is common in continental mountain belts worldwide, including Scandinavia, India, Brazil, and North America. A fresh surface is hard and does not fizz with dilute hydrochloric acid.
