metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used in construction as crushed stone for road beds, in the glass industry, as decorative stone in landscaping, and sometimes as a gemstone if colored by impurities.
Geological facts
Quartzite is so tough that it often survives environmental weathering long after surrounding rocks have eroded, frequently forming the peaks of mountain ranges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture. It is commonly found in metamorphic belts worldwide, such as the Appalachian Mountains.
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