metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or red; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none, breaks with a conchoidal fracture; Specific Gravity: 2.6 - 2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, but can be pink or red
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or red; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none, breaks with a conchoidal fracture; Specific Gravity: 2.6 - 2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). It is found in ancient metamorphic belts globally.
Uses & applications
Used as decorative stone in landscaping, as a crushed stone for road construction and railway ballast, and in the manufacturing of glass and ceramics due to its high silica content.
Geological facts
Quartzite is so hard that it can scratch steel and glass easily. In some regions, ancient hunters used it to create stone tools when flint was unavailable because it breaks with sharp edges.
Field identification & locations
Identify in the field by its extreme hardness and its sugary-looking texture (granoblastic). Unlike marble, it will not fizz when exposed to acid. It is commonly found in mountainous regions or as rounded boulders in riverbeds.
