igneous
Granite Pebble
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Mottled grey, black, and orange/pink; Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Cleavage: Varies by mineral component; Specific Gravity: 2.63-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, black, and orange/pink
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled grey, black, and orange/pink; Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Cleavage: Varies by mineral component; Specific Gravity: 2.63-2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specific specimen has been water-worn into a rounded pebble shape, likely through river or beach erosion over thousands of years.
Uses & applications
In crushed form, it is used for construction and road surfaces. In large slabs, it is used for countertops and monuments. Smooth pebbles are often used in landscaping and garden decor.
Geological facts
Granite makes up a large portion of the continental crust. The pink/orange hues in this pebble are likely due to Potassium Feldspar (Orthoclase), while the dark spots are likely Biotite mica or Hornblende.
Field identification & locations
Identify by its 'salt and pepper' appearance and extreme hardness (it will scratch glass). Commonly found in glacial till, riverbeds, and mountainous regions worldwide.
