metamorphic
Quartzite (or Iron-Stained Quartz)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, brown, yellowish, with translucent milky-white quartz patches. Luster: Vitreous to greasy. Cleavage: None (conchoidal fracture). Specific Gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, brown, yellowish, with translucent milky-white quartz patches. Luster: Vitreous to greasy. Cleavage: None (conchoidal fracture). Specific Gravity: ~2.65.
Formation & geological history
Formed from quartz-rich sandstone subjected to intense heat and pressure during regional metamorphism, fusing quartz grains together. The brownish coloration is due to iron oxide staining during weathering.
Uses & applications
Used as crushed stone in construction, road aggregate, ballast, and occasionally for decorative landscaping or rock collecting.
Geological facts
Quartzite is so tough that when it breaks, it fractures through the quartz grains themselves rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identified by its extreme hardness (scratches glass with ease), grainy sugary texture fused tightly together, and lack of reaction to acid. Commonly found in mountainous regions and stream beds worldwide.
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