metamorphic
Quartzite (with Iron Staining)
Metamorphosed Sandstone (mainly SiO2 with Fe2O3/FeOOH impurities)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Pink to brownish-yellow; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Pink to brownish-yellow
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Pink to brownish-yellow; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the sand grains to recrystallize and fuse together. The yellow/brown color is due to iron oxide staining from weathering.
Uses & applications
Used in construction as road ballast, flooring, and wall coverings. Also used as a decorative stone in landscaping or as a lapidary material.
Geological facts
Quartzite is so tough that it often outlasts the original rock around it, forming prominent ridges and hills. It is often confused with marble but is much harder and will not react with acid.
Field identification & locations
Identified in the field by its grainy texture and its ability to scratch glass. Found globally in ancient mountain belts and shields, particularly in areas like the Appalachians or the Brazilian Shield.
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