igneous
Granite Pebble
Felsic intrusive igneous rock
Hardness: 6-7 (Mohs scale); Color: Mottled white, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspars, none in quartz; Specific gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled white, pink, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled white, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspars, none in quartz; Specific gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. As the magma cools, large crystals of quartz, feldspar, and mica interlock. This specific specimen appears to be water-worn, indicating it was shaped by alluvial or glacial processes.
Uses & applications
Primarily used in large-scale construction, countertops, and monuments; as a small pebble, it is used for landscaping, aquarium gravel, or as a pocket stone for collectors.
Geological facts
Granite is the most common rock found in the Earth's continental crust. Because of its hardness and resistance to erosion, it often forms the core of many mountain ranges worldwide.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in riverbeds and glacial tills across North America and Europe. Tips for collectors: look for variations in feldspar color, ranging from white to deep salmon pink.
