metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink, red, or orange due to iron oxide; Luster: vitreous to dull; Crystal structure: hexagonal (granular texture); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink, red, or orange due to iron oxide; Luster: vitreous to dull; Crystal structure: hexagonal (granular texture); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the original quartz grains to recrystallize into a dense, interlocking mosaic of quartz crystals.
Uses & applications
Used widely in construction as crushed stone for road grit and railway ballast, as a decorative stone in architecture (flooring, wall cladding), and historically for making stone tools due to its hardness and fracturing pattern.
Geological facts
Quartzite is so hard that it will scratch glass. It is often more resistant to weathering than the surrounding rock, often forming prominent ridges or mountain peaks in the landscape.
Field identification & locations
Identify by its ability to scratch glass and its lack of reaction to acid (unlike marble). It is found globally in ancient mountain belts and Canadian, Brazilian, and Western US rock formations. Collectors look for pieces with distinct coloration or visible recrystallization.
