metamorphic
Quartzite
Metamorphic Rock consisting chiefly of Quartz (SiO2)
Hardness: 7 on the Mohs scale. Color: White to light tan/pink. Luster: Vitreous to dull. Crystal structure: Granular, interlocking. Cleavage: None (breaks with conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on the Mohs scale
- Color
- White to light tan/pink
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on the Mohs scale. Color: White to light tan/pink. Luster: Vitreous to dull. Crystal structure: Granular, interlocking. Cleavage: None (breaks with conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartzose sandstone under intense heat and pressure. The original quartz grains recrystallize into a dense, interlocking mosaic of crystals.
Uses & applications
Used in construction as crushed stone for road ballast, as decorative building stone, and historically as a raw material for stone tools (lithics) due to its hardness and fracture patterns.
Geological facts
Quartzite is so hard that it will scratch glass and steel. In some cases, the original sedimentary bedding lines of the sandstone are preserved despite the intense metamorphism.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture. Unlike marble (which it can resemble), it will not react or fizz when exposed to weak acid (HCl). Common in mountain ranges and ancient shields worldwide.
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