igneous
Weathered porphyritic granite pebble
Granite, composed mainly of quartz, feldspar, and mica
AI-generated identification · may be incorrectTypically Mohs 6–7, pale gray to cream with pinkish or brown weathering, and a granular crystalline texture; the rounded surface is naturally weathered and may obscure individual crystals. Specific gravity is about 2.6–2.7, with weak cleavage inherited from feldspar and no true layering.
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Physical properties
Typically Mohs 6–7, pale gray to cream with pinkish or brown weathering, and a granular crystalline texture; the rounded surface is naturally weathered and may obscure individual crystals. Specific gravity is about 2.6–2.7, with weak cleavage inherited from feldspar and no true layering.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic intrusive events; this pebble was later eroded and rounded by water or glacial transport.
Uses & applications
Used extensively as building stone, countertops, paving, aggregate, and monuments; this small specimen has mainly educational or decorative value.
Geological facts
Its light color and visible interlocking mineral grains distinguish it from basalt and most sedimentary rocks. Brown patches commonly represent iron-oxide staining from weathered biotite or feldspar.
Field identification & locations
Look for hard, interlocking grains of translucent quartz, white or pink feldspar, and dark mica; it should scratch glass but not be scratched by a steel knife. Common worldwide, especially in mountainous and glaciated regions.
