metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to grey, can be pink or reddish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white to grey, can be pink or reddish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to grey, can be pink or reddish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogeny). It originated from sedimentary deposits over millions of years.
Uses & applications
Used widely in construction as crushed stone, road ballast, and decorative stone. High-purity quartzite is used to produce silica sand for glassmaking and silicon for electronics.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and hills. It is distinguished from sandstone because it breaks through the grains rather than around them.
Field identification & locations
Found in metamorphic mountain belts globally. To identify in the field, use a glass scratch test (Quartzite will scratch glass) and look for a sugary texture that breaks across mineral grains.
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