metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to grainy; Crystal structure: hexagonal (trigonal); Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to grainy
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to grainy; Crystal structure: hexagonal (trigonal); Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so tough that it often survives intense weathering better than surrounding rocks, frequently forming the tops of ridges and mountains. It is harder than steel.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary appearance. Unlike sandstone, quartzite fractures across its grains rather than around them. Found globally in mountainous regions.
