metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous (glassy) to waxy; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- vitreous (glassy) to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous (glassy) to waxy; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, often during mountain-building events. The individual quartz grains recrystallize into a dense, interlocking mosaic.
Uses & applications
Used in construction as crushed stone or road ballast, as dimension stone for counter tops and flooring, and as a raw material for glass and ceramics manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks on a landscape, forming prominent ridges and hills. It is often confused with marble but can be distinguished because quartzite will not react to acid and is much harder.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of foliation. Often found in mountainous regions or as water-worn pebbles in riverbeds and glacial deposits.
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