metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to grey with light brown/orange iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to grey with light brown/orange iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to grey with light brown/orange iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. These specimens are often found as water-worn pebbles in riverbeds or glacial deposits.
Uses & applications
Used as crushed stone for road construction, railway ballast, and in the production of glass and ceramics. Polished stones are used in landscaping and as decorative pebbles.
Geological facts
Quartzite is so tough that it often survives intense weathering and transport better than other rocks, which is why it is frequently found as rounded river cobbles. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its extreme hardness and sugary or crystalline appearance on a fresh break. It lacks the graininess of sandstone because the pores have been filled. Commonly found in mountainous regions or shifted by glacial activity.
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