metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pinkish-red to grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.63–2.65
- Hardness
- 7 on Mohs scale
- Color
- Pinkish-red to grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pinkish-red to grey; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events. This specimen appears weathered and water-worn.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Highly durable and resistant to weathering.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in high-relief areas. It will scratch glass easily and is often mistaken for chert, though it has a grainy texture.
Field identification & locations
Identify by its extreme hardness and the fact that it breaks across quartz grains rather than around them. Commonly found in metamorphic belts and as pebbles in riverbeds.
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