metamorphic
Blue Quartzite
Quartzite (mostly SiO2 with mineral inclusions)
Hardness: 7 on Mohs scale; Color: Pale blue to greyish-blue; Luster: Vitreous to waxy; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Pale blue to greyish-blue
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Pale blue to greyish-blue; Luster: Vitreous to waxy; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure (metamorphism). The blue color typically comes from inclusions of minerals like dumortierite, magnesioriebeckite, or crocidolite.
Uses & applications
Used as a decorative stone, in jewelry (beads/cabochons), as countertops, and in landscape architecture.
Geological facts
Quartzite is so tough that it often survives intense weathering better than the rocks surrounding it, leading to the formation of ridges and hilltops. Blue varieties are rarer than white or grey counterparts.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and granular crystalline texture. Commonly found in metamorphic mountain belts like the Appalachians or the Alps.
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