metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. The original quartz sand grains recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in glass manufacturing. High-quality slabs are used for kitchen countertops and decorative flooring.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it resists weathering better than surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its grainy, sandpaper-like texture that sparkles slightly. It breaks through the grains, unlike sandstone which breaks around them.
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