metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, with pink/red iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, with pink/red iron staining
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, with pink/red iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, usually during mountain-building events (orogeny).
Uses & applications
Used in construction as crushed stone or road ballast, as a decorative stone in landscaping, and historically for stone tools due to its hardness and durability.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming prominent ridges and peaks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its grainy texture that looks like sandstone but breaks through the grains rather than around them. Often found in ancient mountain belts or as rounded river cobbles.
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