metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: light tan/beige/pinkish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- light tan/beige/pinkish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: light tan/beige/pinkish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Individual quartz grains recrystallize into an interlocking mosaic.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative building stone, and historically for stone tools due to its hardness and durability.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is often confused with marble but can be distinguished because quartzite will scratch glass and marble will not.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel nail) and its grainy, sugary texture. It typically feels much denser and harder than common sandstone.
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