metamorphic
Iron-stained Quartzite
Metamorphosed Quartz (SiO2) with Hematite/Limonite impurities
Hardness: 7 (Mohs scale); Color: Rusty orange, reddish-brown, and translucent white; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Rusty orange, reddish-brown, and translucent white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Rusty orange, reddish-brown, and translucent white; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. The reddish-orange coloring comes from the oxidation (rusting) of iron-bearing minerals that infiltrated the rock through groundwater.
Uses & applications
Used as a decorative stone in landscaping, as a construction aggregate, and occasionally in lapidary work for cabochons or tumbled stones. High-purity quartzite is used in the glass industry.
Geological facts
Quartzite is so tough that it often survives intense erosion that wears away surrounding rock, forming resistant ridges. It is often harder than the steel of a pocket knife.
Field identification & locations
Identify in the field by its sugary texture and inability to be scratched by a steel blade. It will not fizz in contact with acid, distinguishing it from marble. Common in mountain ranges and ancient shield areas.
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