metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, light brown, or tan; 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
- Pink, light brown, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, light brown, or tan; 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, typically in convergent plate boundaries. The sand grains recrystallize and interlock firmly.
Uses & applications
Used as a decorative stone in architecture, as a building material, road ballast, and in the manufacture of glass and ceramics due to its high silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks, remaining as resistant ridges or peaks in mountain ranges. It is harder than steel.
Field identification & locations
Identify in the field by its granular, sugary texture and extreme hardness (it will easily scratch glass). Common in mountain belts like the Appalachians or the Alps.
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