metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with a sugary appearance; Luster: vitreous to dull; Crystal structure: hexagonal; Cleavage: none (fractures across grains)
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan with a sugary appearance
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with a sugary appearance; Luster: vitreous to dull; Crystal structure: hexagonal; Cleavage: none (fractures across grains)
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the sand grains to recrystallize into a interlocking mosaic of quartz crystals. Found in various geological ages during mountain-building events.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in gardens or interior design due to its durability.
Geological facts
Quartzite is so hard that it will scratch glass and is resistant to chemical weathering. If you break it, the fracture cuts through the sand grains rather than around them, which distinguishes it from sandstone.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness. It is commonly found in mountainous regions or glacial deposits. Look for its resistance to breaking and its ability to scratch steel.
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