metamorphic
Quartzite
Quartzite (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish or yellowish tints due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; 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, often with reddish or yellowish tints due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original sand grains to recrystallize and fuse together into a dense, crystalline rock.
Uses & applications
Used extensively in road construction as crushed stone, in railway ballast, for floor tiles, wall coverings, and as a decorative stone in landscaping. High-purity quartzite is used to produce ferrosilicon and industrial silica.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the caprock on ridges or mountains. Unlike sandstone, quartzite fractures across the individual sand grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary or crystalline texture. It is found worldwide in mountainous regions or ancient continental shields where tectonic activity has occurred.
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