metamorphic
Blue Quartzite
Quartzite with inclusions (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-blue to lavender-blue with tan/yellow matrix; Luster: Vitreous to waxy; Structure: Granoblastic (crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Grayish-blue to lavender-blue with tan/yellow matrix
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-blue to lavender-blue with tan/yellow matrix; Luster: Vitreous to waxy; Structure: Granoblastic (crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains and cementing material to recrystallize into an interlocking mosaic. The blue coloration is often due to light scattering (Tyndall effect) caused by tiny inclusions of minerals like dumortierite, crocidolite, or rutile.
Uses & applications
Used primarily as decorative stone, countertops, interior wall cladding, and for landscaping. Minor use in high-end lapidary work and as a collector's specimen due to the unique blue hue.
Geological facts
Blue quartzite is significantly rarer than standard white or gray quartzite. While most quartzite is monotone, the 'blue' variety often contains microscopic needles of other minerals that reflect blue light, similar to why the sky appears blue.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary texture under a lens. It will not react to acid unlike marble. Found in significant deposits in Brazil, South Africa, and parts of the Eastern United States (Blue Ridge Mountains).
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