metamorphic
Quartzite
Quartzite (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink/red (due to iron oxides); Luster: vitreous to dull; Crystal structure: interlocking mosaic of quartz crystals; Cleavage: none (breaks with conchoidal fracture through grains)
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pink/red (due to iron oxides)
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink/red (due to iron oxides); Luster: vitreous to dull; Crystal structure: interlocking mosaic of quartz crystals; Cleavage: none (breaks with conchoidal fracture through grains)
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, creating a much harder rock. It can form in various geological ages during mountain-building events.
Uses & applications
Extensively used as a decorative stone in construction, flooring, wall cladding, and countertops. It is also used as crushed stone for road construction and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the capstone of ridges and mountains because it resists erosion better than the surrounding rock types. It is often confused with marble, but quartzite is much harder and will not react with acid.
Field identification & locations
Identify in the field by its sugary, crystalline appearance when broken; unlike sandstone, it will break through the sand grains rather than around them. It is commonly found in ancient mountain belts across North America (like the Appalachians) and Scandinavia.
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