igneous
Granite (Weathered/Oxidized)
Phaneritic Felsic Igneous Rock (composed of Quartz, Orthoclase Feldspar, and Mica)
Hardness: 6-7 Mohs; Color: Mottled orange-brown (from iron oxidation), gray, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar grains, none in quartz.
- Hardness
- 6-7 Mohs
- Color
- Mottled orange-brown (from iron oxidation), gray, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled orange-brown (from iron oxidation), gray, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar grains, none in quartz.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). The orange/brown staining is due to chemical weathering and the oxidation of iron-bearing minerals, often occurring over millions of years.
Uses & applications
Used widely in construction as dimension stone, aggregates, and countertops. Weathered specimens like this are primarily used for road base, landscaping, or as geological teaching tools.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The pink or orange hue in this specific specimen is likely Limonite or Hematite staining on the potassium feldspar grains.
Field identification & locations
Identify in the field by its 'salt and pepper' crystalline texture and its inability to be scratched by a steel knife. Commonly found in mountainous regions or shield areas like the Appalachians or the Rockies.
