igneous
Granite Water-Worn Pebble
Granite (composed primarily of Quartz, Feldspar, and Mica)
Hardness: 6-7 Mohs; Color: Salt and pepper appearance with gray, translucent quartz, pinkish-tan feldspar, and black biotite/mica flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible grains); Specific gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper appearance with gray, translucent quartz, pinkish-tan feldspar, and black biotite/mica flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible grains); Specific gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic formation). This specific specimen has been smoothed and rounded by river or beach water erosion over thousands of years.
Uses & applications
Used in construction, countertops, and landscaping. Small polished pebbles are used in decorative gravel, aquariums, and rock tumbling kits.
Geological facts
Granite is the primary rock making up the Earth's continental crust. It is one of the hardest and most durable common stones, which is why it resists weathering better than surrounding rocks.
Field identification & locations
Identify by its multi-colored, crystalline texture where individual grains of quartz and feldspar are visible. It will scratch glass and won't react with acid. Commonly found in riverbeds and mountainous regions.
