metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white to light tan/yellow; Luster: vitreous to grainy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- white to light tan/yellow
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light tan/yellow; Luster: vitreous to grainy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure. This recrystallizes the quartz grains into a dense, interlocking mosaic.
Uses & applications
Used in construction as crushed stone or road ballast, as a decorative building stone, and historically for stone tools due to its hardness.
Geological facts
Quartzite is so tough that it often survives intense weathering better than surrounding rocks, frequently forming the caps of ridges and mountain peaks.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, sugary texture. Unlike sandstone, it breaks across the grains rather than around them.
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