metamorphic
Red Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale. Color: Red to reddish-brown due to hematite/iron oxide inclusions. Luster: Vitreous to dull. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Red to reddish-brown due to hematite/iron oxide inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Red to reddish-brown due to hematite/iron oxide inclusions. Luster: Vitreous to dull. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse into a dense, hard rock. Often found in Precambrian or Paleozoic geological formations.
Uses & applications
Used primarily as decorative stone, crushed stone for road construction, railroad ballast, and occasionally in lapidary work for cabochons or garden landscaping.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming prominent ridges and hills. It is often confused with marble, but quartzite is much harder and will not react with acid.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and the way it breaks through the constituent sand grains rather than around them. Common in mountainous regions with deep crustal history.
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