metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: approx 2.6.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: approx 2.6.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). It has a geological age ranging from Precambrian to more recent periods.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative building stone (dimension stone), and in some cases as a source of silica for glass making.
Geological facts
Quartzite is so durable that it often forms the crests of ridges and mountain peaks, resisting erosion much better than the rocks surrounding it. It is often harder than the steel of a knife blade.
Field identification & locations
Identify in the field by its sugary, granular texture and its inability to be scratched by a steel pocketknife. It will not react with acid, distinguishing it from marble. Common in metamorphic belts worldwide.
