metamorphic
Orange Quartzite
Metamorphosed Quartz-arenite (SiO2)
Hardness: 7 (Mohs scale); Color: Orange, peach, or tan; Luster: Vitreous to waxy (when polished); Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Orange, peach, or tan
- Luster
- Vitreous to waxy (when polished)
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Physical properties
Hardness: 7 (Mohs scale); Color: Orange, peach, or tan; Luster: Vitreous to waxy (when polished); Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing recrystallization of quartz grains. Commonly found in ancient mountain belts and Precambrian shields.
Uses & applications
Used as a decorative stone, in jewelry (often tumbled), landscaping, and due to its hardness, as a construction aggregate and ballast.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and hills. When it undergoes metamorphism, the individual sand grains lose their original shape and weld together into a solid mosaic of crystals.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and lack of reaction to acid. Often found in riverbeds as rounded pebbles. Common in Brazil, India, and the United States (Appalachian Mountains).
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