igneous
Granite Pebble
Phaneritic plutonic rock (Quartz-Alkali Feldspar-Plagioclase)
Hardness: 6-7 Mohs; Color: Tan, orange-pink, and black; Luster: Vitreous to dull (water-worn); Structure: Phaneritic (visible crystals); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Tan, orange-pink, and black
- Luster
- Vitreous to dull (water-worn)
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Physical properties
Hardness: 6-7 Mohs; Color: Tan, orange-pink, and black; Luster: Vitreous to dull (water-worn); Structure: Phaneritic (visible crystals); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground, typically within the Earth's continental crust. This specimen has been rounded and smoothed by water erosion.
Uses & applications
Used extensively in construction (crushed stone, countertops, monuments) and as decorative landscaping gravel. Small pebbles like this are common in riverbeds and beaches.
Geological facts
Granite is the primary component of the Earth's continental crust. The black spots in this specimen are likely biotite mica or hornblende, while the tan/orange is orthoclase feldspar.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and its interlocking crystalline texture. It will not be scratched by a steel knife. Common in mountainous regions and glacial deposits.
