metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, orange, or white due to iron oxide staining; Luster: Vitreous to waxy; Structure: Granular, non-foliated crystalline texture; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6–2.7.
- Hardness
- 7 on Mohs scale
- Color
- Pink, orange, or white due to iron oxide staining
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, orange, or white due to iron oxide staining; Luster: Vitreous to waxy; Structure: Granular, non-foliated crystalline texture; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6–2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. Typically found in Precambrian or Paleozoic formations.
Uses & applications
Used as a decorative stone, in construction as crushed stone for road ballast, and as a source of silica for glass making. High-quality pieces are used for countertops and river stone landscaping.
Geological facts
Quartzite is so hard and dense that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent sandstone.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its lack of reaction to acid. Often found as rounded river cobbles or within mountain ranges. Common in many global locations including the Lake Superior region and the Appalachians.
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