metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none, breaks with conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together, typically during mountain-building events (orogeny) in various geological ages from Precambrian to Cenozoic.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and in the manufacturing of glass and ceramics due to high silica content. Occasionally used in jewelry as beads.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in weathering processes, forming prominent ridges and hilltops. It is one of the hardest and most chemically resistant rocks found on the Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its sugary, crystalline texture that breaks across the grains rather than around them. Found globally in metamorphic belts such as the Appalachians, Alps, and Scottish Highlands.
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