metamorphic
Quartzite with Iron Inclusions
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: White to tan with reddish-orange iron staining. Luster: Vitreous to greasy. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to tan with reddish-orange iron staining
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale. Color: White to tan with reddish-orange iron staining. Luster: Vitreous to greasy. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The iron staining occurs when groundwater rich in iron oxide permeates the rock over geological time.
Uses & applications
Used primarily as crushed stone for road construction and railway ballast. High-quality specimens are used for countertops, floor tiles, and as decorative landscaping stones.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers much more slowly than surrounding rocks.
Field identification & locations
Identify it by its ability to scratch glass and its grainy, sugary appearance on fresh breaks. Unlike marble, it will not fizz when exposed to acid. Commonly found in metamorphic belts worldwide.
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