metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, can be pink or reddish; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, can be pink or reddish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, can be pink or reddish; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This process recrystallizes the quartz grains into an interlocking mosaic of crystals. It can date back to any geological era from the Precambrian to more recent tectonic events.
Uses & applications
Used heavily in construction as decorative stone, crushed stone for road beds, and in the manufacturing of glass and ceramics. It is also used as dimension stone for counter tops and wall coverings.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountain ranges, forming the highest peaks and ridges. It is often confused with marble, but unlike marble, it will not react with acid and is significantly harder.
Field identification & locations
Identify it by its extreme hardness (it will easily scratch glass) and its grainy, sugary appearance on fresh breaks. It is found in folded mountain belts and ancient shield regions globally.
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