metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light grey
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); 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).
Uses & applications
Used in construction as road ballast, railway 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 resistant ridges and hilltops in many mountain ranges.
Field identification & locations
Identify by its extreme hardness (it will scratch glass) and its sugary, granular texture. Unlike marble, it does not fizz when in contact with acid.
