metamorphic
Quartzite (Ferruginous)
Quartzite (major component SiO2 with Fe2O3 impurities)
Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, or pink; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown, tan, or pink
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, or pink; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. The reddish hue indicates the presence of iron oxide (hematite) during or after formation.
Uses & applications
Used as crushed stone for road construction and railway ballast; occasionally used as decorative stone in landscaping or for making tools in prehistoric times.
Geological facts
Quartzite is so durable that it often forms the crests of ridges and mountain peaks, as it is more resistant to weathering than the surrounding rock types.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary texture that sparkles in sunlight. Unlike sandstone, when broken, quartzite breaks through the quartz grains rather than around them.
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