igneous
Granite River Rock
Phaneritic Felsic Igneous Rock (Granite)
Hardness: 6-7 Mohs; Color: Gray, tan, and white speckled; Luster: Dull/earthy (weathered surface) to vitreous (on fresh breaks); Texture: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 Mohs
- Color
- Gray, tan, and white speckled
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Physical properties
Hardness: 6-7 Mohs; Color: Gray, tan, and white speckled; Luster: Dull/earthy (weathered surface) to vitreous (on fresh breaks); Texture: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen shows rounding and smoothing indicating it was transported and weathered in a high-energy water environment like a river or glacial stream.
Uses & applications
Used in construction as crushed stone, dimension stone for countertops and monuments, and as decorative landscaping gravel.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because it is so hard and resistant to erosion, it often forms the core of many mountain ranges.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. It will not be scratched by a steel nail. Common globally in crystalline basement rock areas.
