metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxide inclusions); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to pink (due to iron oxide inclusions)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxide inclusions); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in convergent plate boundaries (orogenic belts). It can range from Precambrian to more recent geological ages.
Uses & applications
Used primarily in construction as crushed stone for road beds, railway ballast, and as a decorative building stone or countertop material. High-purity quartzite is used to produce ferrosilicon and industrial silica sand.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it weathers much more slowly than the surrounding rock.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its tendency to break across individual quartz grains rather than around them. Common in the Appalachian Mountains and Lake Superior regions.
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