metamorphic
Red Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-pink to brownish-red; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
- Hardness
- 7 on Mohs scale
- Color
- Reddish-pink to brownish-red
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-pink to brownish-red; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic activity cause sand grains to recrystallize and fuse together. The red color is typically derived from trace inclusions of hematite (iron oxide).
Uses & applications
Used primarily as decorative crushed stone in landscaping, as railway ballast, and in construction as a durable aggregate. High-quality pieces are sometimes used in lapidary work for cabochons or carving.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprocks of hills and ridges because it resists erosion better than the surrounding softer rocks. It can be distinguished from sandstone because it fractures through the sand grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (will scratch glass and steel) and its crystalline, sugary appearance on broken surfaces. It is commonly found in ancient mountain belts like the Appalachian Mountains in the US or the Precambrian shields of Canada and Brazil.
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