metamorphic
Red Quartzite
Quartzite (primarily SiO2 with hematite inclusions)
Hardness: 7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (individual grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to maroon
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (individual grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. The red color is typically due to iron oxide (hematite) present during formation.
Uses & applications
Used as a decorative stone, in construction as crushed stone for road beds, in railway ballast, and occasionally in lapidary work for cabochons or landscaping.
Geological facts
Quartzite is so tough that it often survives intense weathering better than other rocks, frequently forming the tops of ridges and mountains. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness; unlike sandstone, it will break across the sand grains rather than around them. It is commonly found in folded mountain belts like the Appalachians or the Baraboo Range.
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