metamorphic
Quartzite
Quartzite (SiO2 silicon dioxide)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with a vitreous (glassy) luster; Crystal structure: hexagonal/trigonal; Cleavage: none, typically has conchoidal fracture; Specific gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with a vitreous (glassy) luster; Crystal structure: hexagonal/trigonal; Cleavage: none, typically has conchoidal fracture; Specific gravity: approx 2.65.
Formation & geological history
Formed from the regional or contact metamorphism of quartz sandstone. High pressure and temperature cause the quartz grains to recrystallize and fuse together, creating a hard, interlocking structure.
Uses & applications
Extremely useful in construction as crushed stone or decorative facing. High-purity quartzite is used in glassmaking and as a source of silica for metal production. Also popular as countertops and landscaping stone.
Geological facts
Quartzite is so hard that it will scratch glass. In many mountain ranges, quartzite forms the highest peaks because its high resistance to chemical and physical weathering allows it to survive while softer rocks erode away.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness. Unlike marble, it will not fizz with acid. It is commonly found in ancient mountain belts and areas of tectonic activity worldwide.
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