metamorphic
Iron-stained Quartzite / Chert
Silicon Dioxide (SiO2) with Hematite/Limonite impurities
Hardness: 7 (Mohs scale); Color: Rusty orange to reddish-brown (exterior) with potential white or gray core; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Rusty orange to reddish-brown (exterior) with potential white or gray core; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or the chemical precipitation of silica in sedimentary environments. The orange hue is caused by the oxidation of iron minerals (rusting) over thousands to millions of years.
Uses & applications
Used primarily in construction as crushed stone, road ballast, or landscaping rock. High-quality specimens are sometimes used for tumbling or lapidary work.
Geological facts
Quartzite is so hard that it will scratch glass and steel. This specific specimen’s color is a 'stain' rather than its inherent mineral color, similar to how desert varnish forms on rocks in arid climates.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its gritty or waxy texture. It is extremely common in glacial till, riverbeds, and mountainous regions worldwide.
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