igneous
Granite Pebble
Granite (Felsic intrusive igneous rock)
Hardness: 6-7 Mohs; Color: Pink, gray, and black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained) but water-worn; Cleavage: None (fractures); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Pink, gray, and black speckles
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, gray, and black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained) but water-worn; Cleavage: None (fractures); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. This specific specimen is a water-worn river stone or glacial cobble, likely millions of years old, shaped by mechanical weathering in high-energy environments.
Uses & applications
Used widely in construction (countertops, crushed stone, dimension stone) and for decorative landscaping. Small pebbles like this are common in river beds and landscaping gravel.
Geological facts
Granite makes up the majority of Earth's continental crust. The pink color in this specimen indicates a presence of Potassium Feldspar (Orthoclase), while the clear grains are Quartz and dark grains are likely Biotite or Hornblende.
Field identification & locations
Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Commonly found in mountainous regions, riverbeds, and as glacial till throughout North America and Europe.
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