Dumortierite
Other Silicates & Gemstones
Dumortierite is an aluminium borosilicate that commonly forms fibrous or columnar aggregates. Blue and violet-blue are characteristic colors, though green, pink, and red material also occurs; individual crystals can show strong color changes with viewing direction.
Identity
- Material or variety
- Dumortierite
- Scientific or material identity
- Dumortierite
- Classification
- Natural mineral or mineral variety
- Composition or formula
- Al₇BO₃(SiO₄)₃O₃
- Crystal system or structure
- Orthorhombic
- Geological or manufacturing origin
- Can form in more than one geological environment, or combines several materials.
- Mohs hardness
- 7 to 8.5
Origins
Austria · Brazil · France · Madagascar · Namibia · Peru · USA
Appearance & optical properties
dark indigo-blue mineral with fine fibrous striations.
History & discovery
Ferdinand Gonnard first described the mineral in 1881 from a quarry at Chaponost near Lyon, France. He named it for French paleontologist Eugène Dumortier, whose multi-volume research documented Jurassic fossils and rock layers of the Rhône basin.
Uses & care
- Common uses
- Dumortierite is used in high-grade porcelain. Blue massive material is polished for jewelry and carvings and has sometimes been sold in place of lapis lazuli.
- Handling and cleaning
- Dumortierite is hard but brittle and has distinct cleavage. Protect polished pieces from sharp impacts and clean them gently with a soft damp cloth or mild soapy water.
Jewellery
5 pieces of Dumortierite jewellery. Learners earn each one in DigMyGem by learning words; until then it shows as a silhouette.
Blue Quartz Lace Necklace
Necklace
A necklace of polished dumortierite-in-quartz beads, their denim-blue patches threaded like lace through the stone. It is a favourite of collectors of lapidary material.
Denim Lace Ring
Ring
A gold ring set with an oval of blue quartz laced with dumortierite fibres, the blue deepening toward the centre. The stone is often mistaken for sodalite.
Woven Fibre Bangle
Bracelet
A hinged bangle of brushed steel overlaid with thin dumortierite slips, the blue fibres set at angles like woven cloth. It is a modern studio piece.
Indigo Fan Brooch
Brooch
An imagined fan-shaped brooch of dumortierite, the deep denim blue stone, its ribs edged in silver.
Denim Dusk Tiara
Tiara
An imagined silver tiara set with dumortierite, the deep denim-blue stone, in the colour of the sky at dusk.