metamorphic
Orange Quartzite (or Ferruginous Quartz)
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Orange to honey-brown; Luster: Vitreous to greasy; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Orange to honey-brown
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Orange to honey-brown; Luster: Vitreous to greasy; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize into a locked mosaic. The orange color is typically due to iron oxide (hematite/goethite) inclusions or staining.
Uses & applications
Used as decorative stone, in construction as crushed stone or flagstone, and occasionally in lapidary work for cabochons or tumbled stones.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is more resistant to weathering than the sandstone it originated from, often forming the caps of hills and ridges.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it cannot be scratched by a knife). Commonly found in folded mountain belts where tectonic activity has occured.
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