metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to tan/light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to tan/light grey
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: White to tan/light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This causes the original quartz grains to recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and silicate industries. It is also often used for decorative landscaping and interior countertops.
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rocks, forming ridges and resistant hilltops. It is one of the most durable rocks on Earth.
Field identification & locations
Identify it by its extreme hardness (it will scratch glass) and its grainy, sugary look on fresh breaks. It is commonly found in metamorphic belts worldwide, such as the Appalachians or the Alps.
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