metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: Tan, grey, or yellowish. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, grey, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, grey, or yellowish. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, erasing the original sedimentary texture and pore spaces.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and occasionally for making tools or in jewelry as beads.
Geological facts
Quartzite is so tough that it often survives erosion better than the rocks around it, frequently forming the tops of ridges and mountains. It is one of the hardest common rocks found on Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture. Unlike sandstone which breaks around grains, quartzite breaks through the grains. Common in mountainous regions and glacial deposits.
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