metamorphic
Quartzite
Quartzite (SiO₂)
Hardness: 7 on Mohs scale; Color: Grayish-white with some brown staining; Luster: Non-foliated, vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with some brown staining
- Luster
- Non-foliated, vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with some brown staining; Luster: Non-foliated, vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure from tectonic activity. This specimen shows signs of fluvial erosion, having been rounded by water transport.
Uses & applications
Used extensively in construction as road ballast, gravel, and dimension stone. High-purity quartzite is also used to produce silica sand for glassmaking and industrial metallurgy.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is often confused with marble, but can be distinguished because quartzite will scratch glass while marble will not.
Field identification & locations
Identify in the field by its extreme hardness and grainy texture that looks like sandpaper but feels smooth due to the interlocking crystals. Common in mountain ranges and riverbeds globally.
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