metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 (Mohs scale); Color: White, grey, or translucent with sparkly luster; Crystal structure: Non-foliated granoblastic; Cleavage: None/conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, grey, or translucent with sparkly luster
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Physical properties
Hardness: 7 (Mohs scale); Color: White, grey, or translucent with sparkly luster; Crystal structure: Non-foliated granoblastic; Cleavage: None/conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This process causes individual quartz grains to recrystallize and fuse into a solid, durable rock mass.
Uses & applications
Used in construction as crushed stone or decorative facing, in metallurgy as a source of silica, and as a gemstone when containing inclusions or vibrant colors.
Geological facts
Quartzite is so tough that it often survives surface weathering better than surrounding rocks, frequently forming the tops of ridges and hills. It is harder than steel and can easily scratch glass.
Field identification & locations
Look for a sugary, crystalline texture that does not fizz with acid (unlike marble). It is found worldwide in mountain ranges where tectonic activity has buried and transformed ancient beach sands.
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