metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Pinkish-brown or reddish; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Grainy texture with visible fused sand grains.
- Hardness
- 7 (Mohs scale)
- Color
- Pinkish-brown or reddish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Pinkish-brown or reddish; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Grainy texture with visible fused sand grains.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. Often found in Precambrian and Paleozoic rock formations.
Uses & applications
Used in construction as decorative stone, crushed stone for road beds, and railroad ballast. Due to its resistance to heat, it is also used in manufacturing glass and ceramics.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills over millions of years. It reacts very slowly to chemical weathering.
Field identification & locations
Identify by its ability to scratch glass and its lack of reaction to acid. In the field, it often has a sugary texture on fresh surfaces. Commonly found in mountainous regions near fault lines.
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