metamorphic
Quartzite
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: tan, white, or light brownish due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- tan, white, or light brownish due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, white, or light brownish due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into a dense, interlocking mosaic.
Uses & applications
Used extensively in road construction, as railway ballast, for ornamental architecture, and sometimes as a source of silica for glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts surrounding rocks in mountain-building processes, frequently forming the caps of ridges and mountain peaks.
Field identification & locations
Identify by its extreme hardness (scratches glass) and its grainy, sandpaper-like texture that unlike sandstone, breaks across the grains rather than around them. Found globally in ancient mountain belts.
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