metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish; Luster: vitreous (glassy); Crystal structure: trigonal (granular texture); Cleavage: none; Specific gravity: 2.6–2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, but can be pink or reddish
- Luster
- vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish; Luster: vitreous (glassy); Crystal structure: trigonal (granular texture); Cleavage: none; Specific gravity: 2.6–2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. It can originate from many geological eras, often found in mountain belts.
Uses & applications
Used as a decorative stone in construction, for road ballast, and in the manufacturing of glass and ceramics due to its high silica content. Small pieces are used as gravel/landscaping stone.
Geological facts
Quartzite is so tough that it often survives intense weathering better than the rocks surrounding it, forming prominent ridges and hilltops. It is harder than steel and will scratch glass easily.
Field identification & locations
Identify in the field by its extreme hardness and sugary, granular appearance. Unlike sandstone, it will break through the quartz grains rather than around them. It is very common in metamorphic terrains worldwide.
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