metamorphic
Iron-Stained Quartz/Quartzite
Silicon Dioxide (SiO2) with iron oxides (Limonite/Hematite)
Hardness: 7 (Mohs scale); Color: Rusty orange, reddish-brown, and yellow; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Rusty orange, reddish-brown, and yellow
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Rusty orange, reddish-brown, and yellow; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. The distinct coloration is caused by the infiltration of iron-rich fluids into fractures and grains within the rock over geological time.
Uses & applications
Used primarily in road construction as aggregate, in landscaping, and as a low-cost decorative stone. Significant specimens are sometimes used as building facades or in gravel.
Geological facts
This specimen is often called 'Rusty Quartz.' The iron staining is superficial and caused by the oxidation of iron-bearing minerals, similar to the process of rusting metal. It is one of the most durable and weather-resistant rocks on Earth's surface.
Field identification & locations
Identify by its high hardness (it will scratch glass easily), grainy texture (if quartzite), and the presence of reddish-orange stains that do not wash off. Commonly found in mountain belts and riverbeds worldwide.
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