metamorphic
Quartzite with Quartz Vein
Metamorphosed Quartz-rich Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, cream, and grey; Luster: Dull to vitreous; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture)
- Hardness
- 7 on Mohs scale
- Color
- Tan, cream, and grey
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, cream, and grey; Luster: Dull to vitreous; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing recrystallization of quartz grains. The vein indicates a later stage of hydrothermal activity where silica-rich fluids filled a fracture.
Uses & applications
Primarily used as crushed stone for road construction and railway ballast; higher quality specimens are used for architectural stone and countertops.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, frequently forming the tops of ridges and resistant hills.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by steel) and lack of foliation. Commonly found in mountain belts where tectonic forces have compressed sedimentary layers.
