metamorphic
Quartzite
Meta-quartzite
Hardness: 7 on Mohs scale. Color: Light grey, white, buff, with brownish iron oxide staining. Luster: Vitreous to sugary (granoblastic). Crystal structure: Hexagonal/microcrystalline quartz network. Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.63-2.65.
- Hardness
- 7 on Mohs scale
- Color
- Light grey, white, buff, with brownish iron oxide staining
- Luster
- Vitreous to sugary (granoblastic)
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Physical properties
Hardness: 7 on Mohs scale. Color: Light grey, white, buff, with brownish iron oxide staining. Luster: Vitreous to sugary (granoblastic). Crystal structure: Hexagonal/microcrystalline quartz network. Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.63-2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under extreme heat and pressure, causing quartz grains to recrystallize and fuse together seamlessly. Found globally in metamorphic terranes and mountain belts of all geological ages.
Uses & applications
Used extensively as crushed stone in construction, road ballast, decorative landscaping stone, dimension stone for countertops and building facades, and historically for stone tools.
Geological facts
Quartzite is so tough that when it breaks, the fracture cuts directly through the individual quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identified in the field by its extreme hardness (scratches glass easily), sugary texture, and tendency to break across quartz grains rather than around them. Commonly found in stream beds, mountain ridges, and glacial deposits.
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