igneous
Granite Pebble
Phaneritic Felsic Igneous Rock (primarily SiO2, KAlSi3O8, NaAlSi3O8)
Hardness: 6-7 (Mohs scale); Color: Mottled cream, tan, orange, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible interlocking crystals); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled cream, tan, orange, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled cream, tan, orange, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible interlocking crystals); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This particular specimen has been water-worn into a smooth, oval pebble shape, likely over thousands of years in a river or coastal environment.
Uses & applications
Used in landscaping, decorative stone, and construction. Polished pebbles like this are popular for tumbling, massage therapy (hot stones), and as 'worry stones' or decorative accents in vases.
Geological facts
Granite makes up much of the Earth's continental crust. Because it is very hard and resistant to erosion, it often survives as rounded pebbles in streambeds long after softer surrounding rocks have disintegrated.
Field identification & locations
Identified by its speckled 'salt and pepper' appearance and visible crystals of quartz (clear/grey) and feldspar (tan/pink). Commonly found in glacial till, riverbeds, and beach deposits across the globe.
