metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or light brown; Luster: vitreous to grainy; Crystal structure: trigonal system; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or light brown
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or light brown; Luster: vitreous to grainy; Crystal structure: trigonal system; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, where individual quartz grains recrystallize into an interlocking mosaic.
Uses & applications
Used widely in construction as crushed stone for roadbeds and railroad ballast, as roofing granules, and as a decorative stone in architecture and landscaping.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the tops of ridges and mountains. It is harder than steel and will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and grainy texture that resembles sandpaper but cannot be rubbed off. Found globally in mountainous regions and metamorphic terranes.
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