metamorphic
Quartzite
Quartzite (composed primarily of Silica, SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellow (due to impurities); Luster: vitreous to waxy; Texture: granular, non-foliated; Cleavage: none; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or yellow (due to impurities)
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellow (due to impurities); Luster: vitreous to waxy; Texture: granular, non-foliated; Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the individual quartz grains recrystallize and fuse together, creating an extremely hard and durable rock.
Uses & applications
Extremely useful in construction as crushed stone for road aggregates and railroad ballast. Due to its hardness and durability, it is also used for floor tiles, stairs, counter tops, and decorative stones in landscaping.
Geological facts
Quartzite is so hard that it will scratch glass and even tool steel. In the Stone Age, it was occasionally used as a substitute for flint to create projectile points and scrapers, though it is more difficult to flake.
Field identification & locations
Identified in the field by its sugary, granular appearance and its inability to be scratched by a steel nail. Unlike sandstone, quartzite breaks through the quartz grains rather than around them. It is commonly found in mountain ranges and ancient shield areas like the Appalachians or the Canadian Shield.
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