metamorphic
Quartzite
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: white to light grey; Luster: vitreous to dull; Crystal structure: Hexagonal (though interlocking grains in quartzite); Cleavage: None, fractures conchoidally; Specific Gravity: 2.65
- 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: Hexagonal (though interlocking grains in quartzite); Cleavage: None, fractures conchoidally; Specific Gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This process causes individual quartz grains to recrystallize into a dense, interlocking mosaic of crystals.
Uses & applications
Used widely in construction as crushed stone for road ballast, as a building stone, and in the manufacturing of glass and ceramics due to its high silica content.
Geological facts
Quartzite is so tough that it often survives weathering better than surrounding rocks, forming ridges and mountain peaks. It will scratch glass easily, helping distinguish it from similar-looking soft minerals like calcite.
Field identification & locations
Identifiable by its sugary texture and extreme hardness. It won't fizz with acid. Found globally in ancient mountain belts and metamorphic terrains. Common in riverbeds as rounded white cobbles.
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