metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, may appear pink or red due to iron impurities; Luster: vitreous to dull; Crystal Structure: Trigonal (as quartz grains); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, may appear pink or red due to iron impurities; Luster: vitreous to dull; Crystal Structure: Trigonal (as quartz grains); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize into a dense, interlocking mosaic of crystals.
Uses & applications
Used as a decorative stone in architecture, as a raw material for glass manufacturing, in railway ballast, and occasionally in jewelry as or for lapidary work.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the peaks of mountain ranges because it weathers more slowly than the surrounding rock types.
Field identification & locations
Identify by its ability to scratch glass and its sugary, granular texture. Unlike marble, it will not fizz when exposed to weak acid. It is commonly found in fold mountain belts.
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