metamorphic
Quartzite
Quartzite (SiO2 dominant)
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish due to iron oxides; Luster: vitreous to grainy; Crystal structure: Non-foliated interlocking quartz grains; Specific gravity: approx. 2.6
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or reddish due to iron oxides
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish due to iron oxides; Luster: vitreous to grainy; Crystal structure: Non-foliated interlocking quartz grains; Specific gravity: approx. 2.6
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, often in ancient mountain-building events (Orogeny).
Uses & applications
Used in construction as crushed stone or decorative facing; as gravel for road ballast; and in the manufacturing of glass and ceramics due to high silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming resistant ridges or mountain peaks. It will break across the original sand grains rather than around them.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by steel) and lack of foliation compared to gneiss. Found globally in Precambrian shields and mountain belts.
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