metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: White to greyish-white with brownish-yellow iron oxide staining; Luster: Vitreous to greasy; Crystal Structure: Trigonal (microcrystalline interlocked quartz grains); Cleavage: None (conchoidal to uneven fracture); Specific Gravity: ~2.65
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: White to greyish-white with brownish-yellow iron oxide staining; Luster: Vitreous to greasy; Crystal Structure: Trigonal (microcrystalline interlocked quartz grains); Cleavage: None (conchoidal to uneven fracture); Specific Gravity: ~2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing the individual quartz grains to recrystallize and fuse together into a dense, hard rock matrix.
Uses & applications
Used widely in construction as crushed stone for road base, railway ballast, and concrete aggregate. High-purity quartzite is also used to produce silicon metal, ferrosilicon, and glass, as well as decorative dimension stone.
Geological facts
Quartzite is so hard and tough that when it breaks, it fractures right through the quartz grains rather than around them, unlike sandstone. It is highly resistant to chemical weathering and erosion, often forming prominent ridges and hilltops.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily) and sugary to glassy granoblastic texture. Found worldwide in mountainous areas and ancient shield formations such as the Appalachian Mountains and the Canadian Shield.
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