metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal system (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal system (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
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. The geological age can range from Precambrian to Cenozoic depending on the source formation.
Uses & applications
Used as crushed stone for road construction, railroad ballast, and decorative building stone. High-purity quartzite is used in the manufacturing of glass and silicon metal.
Geological facts
Quartzite is so hard and dense that when it breaks, it breaks through the quartz grains rather than along the boundaries between them, unlike its parent stone, sandstone. It is resistant to chemical weathering.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and its sugary, crystalline texture. It is commonly found in mountain ranges or as water-worn pebbles in riverbeds and beaches.
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