metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: yellowish-tan with brownish iron staining; Luster: vitreous to waxy; Structure: granular/crystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- yellowish-tan with brownish iron staining
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-tan with brownish iron staining; Luster: vitreous to waxy; Structure: granular/crystalline; Cleavage: none (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 quartz grains to recrystallize and fuse together.
Uses & applications
Used in glassmaking, as a decorative stone in landscaping, crushed stone for road construction, and occasionally for primitive tools in prehistoric times.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along the boundaries between them, unlike its parent sandstone.
Field identification & locations
Identify by its hardness (it will scratch glass) and lack of reaction to acid. Commonly found in mountain ranges and river gravel deposits globally where ancient sedimentary beds were squeezed.
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