igneous
Granite Pebble
Granite (composition of Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 Mohs; Color: Mottled gray, pink, white, and black; Luster: Vitreous to dull; Crystal Structure: Phaneritic (visible crystals); Cleavage: Feldspars show two planes at 90 degrees; Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Mottled gray, pink, white, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled gray, pink, white, and black; Luster: Vitreous to dull; Crystal Structure: Phaneritic (visible crystals); Cleavage: Feldspars show two planes at 90 degrees; Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. High in silica and alkali metal oxides. This specimen has been rounded by water erosion (alluvial/river action).
Uses & applications
Used in construction, countertops, monuments, and as decorative gravel or river rock for landscaping.
Geological facts
Granite is the primary constituent of Earth's continental crust. Over 80% of Earth's granite is found in the continental plates rather than the oceanic basins.
Field identification & locations
Identify by its 'salt and pepper' appearance and hardness (cannot be scratched by steel). Found globally in mountain ranges and riverbeds. Look for quartz (translucent) and feldspar (colored opaque) minerals.
