igneous
Granite Pebble
Intrusive Felsic Igneous Rock (primarily SiO2 with Al2O3, K2O, Na2O)
Hardness: 6-7 (Mohs scale); Color: Mottled gray, pink, and white with black specks; Luster: Dull (weathered/tumbled) to vitreous (on fresh breaks); Structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (fractures irregularly); Specific Gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled gray, pink, and white with black specks
- Luster
- Dull (weathered/tumbled) to vitreous (on fresh breaks)
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled gray, pink, and white with black specks; Luster: Dull (weathered/tumbled) to vitreous (on fresh breaks); Structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (fractures irregularly); Specific Gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow cooling and solidification of magma deep within the Earth's crust (plutonic formation). This specimen shows signs of mechanical weathering and transport by water (fluvial or glacial action), rounding its sharp edges into a smooth pebble shape.
Uses & applications
In bulk: used for construction aggregate, road base, and dimension stone (countertops). As a single pebble: primarily used for landscaping, garden decor, or as a pocket stone for amateur collectors.
Geological facts
Granite makes up the majority of the Earth's continental crust. The pink color in this specimen is likely due to potassium feldspar (orthoclase), while the white/gray translucent parts are quartz.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally across all continents, especially in mountain ranges and riverbeds downstream from igneous outcrops. Collectors can identify it by its inability to be scratched by a steel knife.
