metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to pink (due to iron oxides)
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, causing quartz grains to recrystallize and fuse together. The coloration suggests the presence of hematite or other iron minerals within the original sandstone mother rock.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative stone in architecture (flooring, wall coverings), and as a raw material for silica in various industrial manufacturing processes.
Geological facts
Quartzite is so tough that it often survives intense weathering that wears away softer surrounding rocks. Throughout history, it has been used to make stone tools because it breaks with a conchoidal fracture similar to flint.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and its crystalline appearance where the grains look fused rather than cemented. Common in mountain ranges and ancient shield regions globally.
