metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Yellowish-tan with orange/red iron staining; Luster: Vitreous to waxy (especially when polished); Crystal Structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Yellowish-tan with orange/red iron staining
- Luster
- Vitreous to waxy (especially when polished)
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellowish-tan with orange/red iron staining; Luster: Vitreous to waxy (especially when polished); Crystal Structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize into a dense interlaced structure. Typically found in mountain belts where tectonic activity occurs.
Uses & applications
Used as a decorative stone, in construction as crushed stone or road ballast, as a high-silica raw material in manufacturing, and commonly as tumbled river stones for landscaping and hobbyist collections.
Geological facts
Quartzite is so hard that it will scratch glass and even steel. It is often more resistant to weathering than the surrounding rock, often forming hills or ridges.
Field identification & locations
Identify in the field by its hardness (it will not be scratched by a knife) and its grainy, sugary look if broken. It often has a smooth, rounded appearance when found in riverbeds or on beaches.
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