igneous
Granite Pebble
Granite (Felsic intrusive igneous rock)
Hardness: 6-7 (Mohs scale); Color: Mottled gray, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled gray, pink, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled gray, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. This specific specimen has been rounded by fluvial (water) or glacial erosion, likely dating from the Precambrian to Cenozoic eras depending on its regional source.
Uses & applications
Used in construction, gravel, landscaping, and as a decorative stone. Large deposits are quarried for countertops and monuments.
Geological facts
Granite makes up a large part of the Earth's continental crust. These rounded pebbles are often called 'river rocks' and are durable enough to survive thousands of miles of travel in water systems.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz (clear/white), feldspar (pink/white), and mica (black). Commonly found in riverbeds, glacial tills, and mountainous regions.
