metamorphic
Quartzite
Quartzite (composed primarily of Silica, SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow or red iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); specific gravity: 2.6 - 2.65.
- 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 yellow or red iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); specific gravity: 2.6 - 2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize into a dense interlocking mosaic.
Uses & applications
Used extensively in construction as road ballast, gravel, and dimension stone. High-purity quartzite is used to produce glass and ferrosilicon for industrial manufacturing.
Geological facts
Quartzite is so durable that it can survive extreme weathering; it often forms prominent ridges or hilltops because it resists erosion better than the rocks surrounding it.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, granular texture. Unlike marble, it will not react with acid. Commonly found in folded mountain belts globally.
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