metamorphic
Quartzite
Quartzite (principally Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.63–2.65
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, typically during mountain-building events. The original quartz sand grains recrystallize into a dense, interlocking mosaic.
Uses & applications
Used extensively in road construction, as railroad ballast, for floor tiles, and as decorative stone in countertops and landscaping. High-purity quartzite is used to produce silica sand for glass making.
Geological facts
Quartzite is one of the most physically durable and chemically resistant rocks found at the Earth's surface. It is so tough that it often forms the caps of ridges and mountains because it resists weathering better than the surrounding rock.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass) and its sugary finish. Unlike marble, which it resembles, it will not fizz when exposed to acid. Found globally in ancient mountain belts and shield areas.
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