Dumortierite is best known in its massive form. That makes it an attractive violet and blue decorative stone when polished. Reddish brown and red varieties also occur. Prismatic crystals larger than 1mm are very rare. Dumortierite is also found inter-grown with rock crystal quartz. It is then called dumortierite quartz. The stone is usually cut en cabochon or polished to make decorative stones.
The surface of dumortierite has a splintery surface and may become pitted when polished. The rough dumortierite crystal shows a distinctive deep blue color. It is common to carve the stone to make decorative objects like water bottles and bowls.
Dumortierite is named after the French scientist, M.E. Dumortier.
Occurrence
Most of the gem-quality variety of dumortierite is found in Nevada (USA). Other localities include Italy, Namibia, Poland, Canada, Sri Lanka, Norway, France, and Madagascar.
Dumortierite Properties
- Specific Gravity: 3.28
- Refractive Index: 1.69-1.72
- Birefringence (DR): 0.037
- Luster: Vitreous
- Crystal Structure: Orthorhombic
- Composition: Aluminum iron borosilicate
- Hardness: 7
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