metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey with reddish-brown iron staining; Luster: Vitreous to sugary; Crystal structure: Non-foliated, interlocking quartz grains; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light grey with reddish-brown iron staining
- Luster
- Vitreous to sugary
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey with reddish-brown iron staining; Luster: Vitreous to sugary; Crystal structure: Non-foliated, interlocking quartz grains; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. High pressure and temperature cause the sand grains to recrystallize and fuse together. Often found in Precambrian or Paleozoic geological formations.
Uses & applications
Used in construction as crushed stone for road ballast, as decorative building stone, in the production of glass and ceramics, and as a refractory material due to its high heat resistance.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it belongs to, forming prominent ridges known as monadnocks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel) and its failure to fizz with acid. Unlike sandstone, when quartzite breaks, the fracture passes through individual grains rather than around them. Found globally in mountainous regions.
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