metamorphic
Orange Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Orange to pinkish-orange; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None; Specific gravity: 2.63–2.65
- Hardness
- 7 on Mohs scale
- Color
- Orange to pinkish-orange
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Orange to pinkish-orange; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None; Specific gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, often during mountain-building events (orogeny).
Uses & applications
Used as a decorative stone, in construction as crushed stone or flooring, and in lapidary for tumbled stones or cabochons.
Geological facts
Quartzite is so durable that it often remains as ridges or peaks when surrounding softer rocks erode away. It is often confused with marble but is much harder and will not react with acid.
Field identification & locations
Identify in the field by its hardness (it scratches glass) and its sugary, granular appearance that breaks across the quartz grains rather than around them. Common in metamorphic belts worldwide.
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