metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey; 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 light grey
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. Found in mountain belts and Precambrian shield areas.
Uses & applications
Used extensively in construction as crushed stone for road gravel and railway ballast. Also used as dimension stone for wall coverings and flooring, and in the production of silica glass.
Geological facts
Quartzite is so tough that it often survives intense weathering better than surrounding rocks, frequently forming the crests of ridges and mountains. It is differentiate from sandstone because it breaks across the grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture. Common in Appalachian Mountains and Lake Superior region.
