metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, white, or gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, white, or gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, white, or gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing recrystallization into an interlocking network of quartz grains.
Uses & applications
Used in construction as crushed stone or road ballast, as dimension stone for counter tops and flooring, and as a source of silica for glass manufacturing.
Geological facts
Quartzite is so durable that it can survive long-term weathering on Earth's surface more effectively than many other rocks, often forming the resistant ridges of mountain ranges.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It is commonly found in ancient mountain belts and metamorphic terrains globally.
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