metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Typically white to gray, but can be pink, red, or purple due to iron impurities; Luster: Greasy to vitreous; Crystal structure: Interlocking quartz crystals (non-foliated); Cleavage: None (fractures conchoidally); Specific gravity: 2.65 - 2.70
- Hardness
- 7 on Mohs scale
- Luster
- Greasy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Typically white to gray, but can be pink, red, or purple due to iron impurities; Luster: Greasy to vitreous; Crystal structure: Interlocking quartz crystals (non-foliated); Cleavage: None (fractures conchoidally); Specific gravity: 2.65 - 2.70
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and pressure, typically during tectonic mountain-building events. Can date from various geological eras, from Precambrian to Cenozoic.
Uses & applications
Used in construction, as a decorative stone, in countertops, for railway ballast, and in the production of silica brick and ferrosilicon.
Geological facts
Unlike sandstone, which breaks around the sand grains, quartzite breaks straight through the quartz grains because of the extreme heat and pressure welding them together. It is extremely durable and resistant to weathering.
Field identification & locations
Identified in the field by its hardness (scratches glass easily), lack of reaction to acid, and sugary, interlocking crystalline texture visible on freshly broken surfaces. Common locations include the Appalachian Mountains in North America, parts of Europe, and Brazil.
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