metamorphic
Red Quartzite
Metamorphic Rock (rich in SiO2 with hematite inclusions)
Hardness: 7 on Mohs scale; Color: Maroon to reddish-brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Maroon to reddish-brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Maroon to reddish-brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. The red color is typically due to the presence of iron oxide (hematite) during formation.
Uses & applications
Used as decorative stone in landscaping, as a construction aggregate, for railroad ballast, and occasionally for primitive stone tools due to its hardness and fracture pattern.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountainous areas, forming prominent ridges. It is often confused with marble, but can be distinguished because quartzite will scratch glass while marble will not.
Field identification & locations
Identify in the field by its extreme hardness and grainy texture that breaks across grains rather than around them. Common in folded mountain belts and ancient shield areas like the Upper Midwest USA (Sioux Quartzite).
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