metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: approx. 2.65.
- Color
- typically white, gray, or tan
- Luster
- vitreous to dull
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Physical properties
Hardness 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: approx. 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. This specimen appears water-worn, suggesting a secondary transport phase in a river or beach environment.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative stone in architecture (flooring/countertops), and sometimes as a source of silica for glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts its parent rock during erosion, forming resistant ridges or mountaintops. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its sugary, granular texture and extreme hardness. It won't react with acid (unlike marble) and will scratch a pocket knife blade. Common globally in metamorphic terrains.
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