metamorphic
Pyritic Quartzite
Metequartzite with FeS2 (Pyrite) inclusions
Hardness: 6-7 on Mohs scale; Color: Yellowish-gold to metallic brassy tan; Luster: Vitreous to sub-metallic; Crystal structure: Hexagonal (quartz) / Isometric (pyrite); Cleavage: None/Indistinct.
- Hardness
- 6-7 on Mohs scale
- Color
- Yellowish-gold to metallic brassy tan
- Luster
- Vitreous to sub-metallic
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Yellowish-gold to metallic brassy tan; Luster: Vitreous to sub-metallic; Crystal structure: Hexagonal (quartz) / Isometric (pyrite); Cleavage: None/Indistinct.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. The metallic sheen suggests secondary mineralization of iron sulfides (pyrite) during or after the metamorphic process, often in hydrothermal environments.
Uses & applications
Primarily used as construction aggregate or decorative stone. High-purity quartzite is used in glass making or as a source of silica in industry.
Geological facts
Quartzite is so tough that when it breaks, it fractures through the quartz grains rather than along their boundaries. The presence of pyrite can cause 'gold fever' in amateur prospectors, though it is often called Fool's Gold.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that sparkles in the sun. Found common in mountain ranges like the Appalachians or the Rockies.
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