metamorphic
Red Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: reddish-brown to pink due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- reddish-brown to pink due to iron oxide impurities
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: reddish-brown to pink due to iron oxide impurities; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. The original sand grains recrystallize into an interlocking mosaic of quartz crystals. Most specimens are from the Proterozoic or Paleozoic eras.
Uses & applications
Used as crushed stone for road construction, railroad ballast, and high-quality specimens are used for architectural decorative stone and landscaping.
Geological facts
Quartzite is so tough that it usually breaks through the sand grains rather than around them, unlike sandstone. Red quartzite is often associated with the 'Baraboo Quartzite' or 'Sioux Quartzite' formations in the United States.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass or steel) and sugary, granular surface that does not rub off. Common in glacial till and riverbeds throughout the Midwest US.
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