igneous
Granite Pebble with Quartz/Mafic Vein
Felsic Igneous Rock (Granitic)
Hardness: 6-7 Mohs; Color: Pink, orange-red, and grey; Luster: Vitreous to dull; Structure: Phaneritic (crystalline) with a distinct cross-cutting vein; Cleavage: None (conchoidal fracture in quartz components)
- Hardness
- 6-7 Mohs
- Color
- Pink, orange-red, and grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, orange-red, and grey; Luster: Vitreous to dull; Structure: Phaneritic (crystalline) with a distinct cross-cutting vein; Cleavage: None (conchoidal fracture in quartz components)
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. The distinct band is a hydrothermal vein, created when mineral-rich fluids filled a fracture in the cooling rock. Most granitic rocks range from 500 million to over 2 billion years old depending on the regional shield.
Uses & applications
Used primarily as decorative landscaping stone, river rock, or for aggregate in construction. High-quality unweathered granite is used for countertops and monuments.
Geological facts
The pink color is caused by potassium feldspar (orthoclase). Granite makes up much of the Earth's continental crust and is exceptionally durable against weathering.
Field identification & locations
Identify by its 'salt and pepper' crystalline texture and pinkish hue. These are extremely common in riverbeds, glacial tills, and mountainous regions throughout North America and Europe.
