metamorphic
Blue Quartz (Dumortierite Quartz)
Silicon Dioxide with Aluminum Borosilicate (SiO2 + AlAl6BSi3O18)
Hardness: 7 Mohs; Color: Light to medium blue inclusions in a grayish-white matrix; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 2.65-2.67
- Hardness
- 7 Mohs
- Color
- Light to medium blue inclusions in a grayish-white matrix
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 Mohs; Color: Light to medium blue inclusions in a grayish-white matrix; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 2.65-2.67
Formation & geological history
Formed in regional metamorphic zones where silica-rich fluids interact with aluminum and boron; the blue color is typically caused by inclusions of the mineral Dumortierite.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons and beads), decorative carvings, and as a collector specimen.
Geological facts
Natural blue quartz is relatively rare compared to other types of quartz. Most blue in quartz is produced by Rayleigh scattering from tiny inclusions rather than chemical substitution in the lattice.
Field identification & locations
Identify in the field by its distinct speckling (unlike the solid color of chalcedony) and its inability to be scratched by steel. Found in Brazil, South Africa, and Virginia (USA).
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