metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light gray with yellowish-brown iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Fracture: Conchoidal to irregular.
- Hardness
- 7 on Mohs scale
- Color
- White to light gray with yellowish-brown iron staining
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light gray with yellowish-brown iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Fracture: Conchoidal to irregular.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during regional mountain-building events (orogeny).
Uses & applications
Used primarily as crushed stone for road construction and railway ballast; also used in decorative architecture and as a source of silica for glass manufacturing.
Geological facts
Quartzite is so durable that it often forms the resistive caprock on mountain ridges, outlasting the softer rocks around it through millions of years of erosion.
Field identification & locations
Identifiable by its ability to scratch glass and its granular, sugary texture. Unlike sandstone, quartzite fractures through the quartz grains rather than around them. Found globally in ancient mountain belts.
