metamorphic
Quartzite (Banded)
Metamorphosed Sandstone (SiO2 with impurities)
Hardness: 7 on Mohs scale; Color: Grey, pink, and green bands; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grey, pink, and green bands
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grey, pink, and green bands; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically during tectonic plate collisions. This specimen shows water-worn rounding, suggesting it was recovered from a riverbed or beach.
Uses & applications
Primarily used in construction for road ballast, roofing granules, and as a decorative stone in landscaping or lapidary work.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the tops of ridges and mountains. The banding reflects the original sedimentary layers of the parent sandstone.
Field identification & locations
Identify by its extreme hardness (it will scratch glass and steel) and its grainy, sugary texture under a lens. Common in ancient mountain belts like the Appalachians or the Canadian Shield.
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