metamorphic
Red Quartzite
Quartzite (Silicon Dioxide with Iron Oxide impurities, SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-pink to brownish-red; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7.
- 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/Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed via the metamorphism of quartz-rich sandstone under intense heat and pressure, causing recrystallization of quartz grains. The red color suggests the presence of hematite or other iron oxides during formation. Found in ancient mountain belts and shield areas dating back to the Precambrian or Paleozoic eras.
Uses & applications
Used as decorative stone in landscaping, road ballast, railway tracks, building stone, and occasionally for lapidary work or inexpensive jewelry when highly saturated in color.
Geological facts
Quartzite is so hard and durable that it often forms the caps of ridges and mountains because it resists erosion better than the surrounding softer rocks. It is distinct from sandstone because it will break through the quartz grains rather than around them.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by steel) and its crystalline, sugary appearance on fresh surfaces. Common in regions with high metamorphic activity like the Appalachians or the Scottish Highlands.
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