metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: Grainy white, grey, or tan; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grainy white, grey, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grainy white, grey, or tan; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together into a dense, hard rock. Can be found in mountain belts worldwide.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and in the manufacturing of glass and ceramics due to high silica content.
Geological facts
Quartzite is so hard that it can scratch steel and glass. It is often more durable than the parent sandstone it originated from, frequently forming prominent ridges and hills because it resists weathering.
Field identification & locations
Identify by its hardness (it will scratch glass) and its sugary, granular texture. It breaks across the grains rather than around them, unlike sandstone. Widely available in glaciated regions and riverbeds.
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