igneous
Granite pebble
Granite; predominantly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, speckled light gray-green and black, with a granular texture and vitreous-to-dull luster; Mohs hardness about 6–7, no consistent cleavage as a whole, and specific gravity roughly 2.63–2.75.
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Physical properties
Coarse-grained, speckled light gray-green and black, with a granular texture and vitreous-to-dull luster; Mohs hardness about 6–7, no consistent cleavage as a whole, and specific gravity roughly 2.63–2.75.
Formation & geological history
An intrusive igneous rock crystallized slowly from silica-rich magma deep in Earth’s crust, commonly during Precambrian to Phanerozoic mountain-building events; this specimen has been naturally worn or manually shaped.
Uses & applications
Used extensively as building stone, countertops, paving, monuments, aggregate, and decorative tumbled material; generally modest collector value.
Geological facts
Its visible interlocking crystals indicate slow underground cooling; black grains are likely biotite or hornblende, while translucent grains are quartz.
Field identification & locations
Identify it by its coarse interlocking crystals, quartz sparkle, feldspar-rich pale matrix, and inability to scratch quartz with a steel knife; common worldwide, especially in continental mountain belts.
