metamorphic
Iron-stained Quartzite
Quartzite with Limonite/Hematite staining (SiO2 with FeO(OH)·nH2O)
Hardness: 7 (Mohs scale); Color: Rusty orange, yellow-brown, grey; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 7 (Mohs scale)
- Color
- Rusty orange, yellow-brown, grey
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Rusty orange, yellow-brown, grey; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure. The orange coloration is a result of secondary iron oxide staining (limonite or rust) from groundwater infiltration over geological time.
Uses & applications
Used primarily as aggregate in construction, road ballast, and occasionally as decorative stone or landscaping rock due to its durability and color.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of hills and ridges. The orange staining is often only surface-deep or follows internal fractures.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that has been fused into a solid mass. Frequently found in riverbeds or mountain outcroppings.
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