metamorphic
Blue Quartzite
Quartzite (primarily SiO2 with inclusions)
Hardness: 7 on Mohs scale; Color: Grayish-blue to slate blue with white streaks; Luster: Vitreous to waxy; Structure: Non-foliated granular; Specific Gravity: 2.6 - 2.8.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-blue to slate blue with white streaks
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-blue to slate blue with white streaks; Luster: Vitreous to waxy; Structure: Non-foliated granular; Specific Gravity: 2.6 - 2.8.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. The blue color often comes from inclusions of blue minerals like crocidolite (dumortierite) or structural 'Rayleigh scattering' of light within the crystals.
Uses & applications
Used for decorative landscaping, architectural stone, crushed stone for road construction, and occasionally for lapidary work or semi-precious jewelry.
Geological facts
Quartzite is tougher than its parent rock, sandstone. It is so hard that it can easily scratch glass and steel. Blue varieties are much rarer than the common white, gray, or pink forms.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy, sugary texture under a lens. Common in ancient mountain belts in regions like Brazil, Scandinavia, and parts of the Appalachian Mountains.
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