igneous
Granite pebble
Granite, chiefly quartz, alkali feldspar, plagioclase, and mica
AI-generated identification · may be incorrectMedium- to coarse-grained, speckled gray-and-white appearance with black mica or amphibole; typically Mohs 6–7, nonmetallic luster, granular interlocking crystals, and no cleavage as a whole. Specific gravity is about 2.63–2.75.
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Physical properties
Medium- to coarse-grained, speckled gray-and-white appearance with black mica or amphibole; typically Mohs 6–7, nonmetallic luster, granular interlocking crystals, and no cleavage as a whole. Specific gravity is about 2.63–2.75.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma deep underground, commonly during Precambrian to Phanerozoic mountain-building events; this rounded specimen was likely transported and weathered by water or ice.
Uses & applications
Used extensively as dimension stone, countertops, paving, monuments, aggregate, and decorative landscaping material; ordinary pebbles have little jewelry value.
Geological facts
Granite’s visible crystals indicate slow cooling, while its rounded shape indicates abrasion after erosion from an exposed outcrop.
Field identification & locations
Identify it by its interlocking gray, white, and black grains, hardness, and lack of layering or bubbles; common worldwide, especially in continental shields and mountain belts. A hand lens can distinguish quartz from feldspar and mica.
