metamorphic
Quartzite
Quartzite (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: white to light tan; Luster: vitreous to dull; Crystal structure: trigonal (granular texture); Cleavage: none (conchoidal fracture through grains); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white to light tan
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light tan; Luster: vitreous to dull; Crystal structure: trigonal (granular texture); Cleavage: none (conchoidal fracture through grains); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during tectonic mountain-building events. The original quartz grains recrystallize into a dense, interlocking mosaic of crystals.
Uses & applications
Used extensively in road construction, as railway ballast, for architectural stone, and as a source of silica for glass manufacturing and electronics.
Geological facts
Quartzite is so durable that it often survives erosion to form the tops of prominent mountain ridges. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary appearance. Unlike sandstone, which breaks around grains, quartzite breaks through the quartz grains. Common in folded mountain belts globally.
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