metamorphic
Iron-Stained Quartzite
Recrystallized Meta-Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown due to iron oxide staining; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal to uneven fracture).
- Hardness
- 7 on Mohs scale
- Color
- Tan to reddish-brown due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown due to iron oxide staining; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal to uneven fracture).
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize into a dense interlaced structure. The iron oxides likely infiltrated through groundwater in a sedimentary or weathering environment.
Uses & applications
Used extensively in the construction industry as crushed stone for road base, railway ballast, and as a dimension stone for flooring or wall cladding. Pure varieties are used to produce silica sand for glass manufacturing.
Geological facts
Quartzite is so durable that it often forms the caps of ridges and mountains because it resists weathering much better than the surrounding rock. It is often tougher than the parent sandstone and will break across grain boundaries rather than around them.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by a steel knife) and its grainy, crystalline appearance that sparkles slightly in direct light. Common in metamorphic belts worldwide. Collectors look for unique staining patterns or mineral inclusions.
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