What is Dumortierite?
Dumortierite is a hard aluminium borosilicate that commonly forms blue fibrous aggregates and attractive ornamental quartz-bearing material.
Mineralogy and structure
The reference formula is Al7BO3(SiO4)3O3. Dumortierite is orthorhombic and often occurs as fine fibres embedded in quartz. Blue colour is commonly linked to trace iron and titanium.
Colour and appearance
Typical colours include blue, violet, pink, brown, green. Its fibrous, prismatic, massive habit and vitreous, pearly lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Dumortierite forms in or is associated with aluminium-rich metamorphic rocks, pegmatites and high-temperature boron-bearing environments. Important documented localities include France, Brazil, Madagascar, the United States, Canada and Sri Lanka.
Collecting and care
Dumortierite is best kept as a labelled reference or collector specimen. Protect fragile crystals from impact and avoid cutting or grinding unknown material. Lead-, arsenic-, vanadium- and copper-bearing specimens are for display and careful handling only.
Dumortierite in popular symbolism
Some modern crystal guides associate Dumortierite with zodiac signs or symbolic themes based on colour, locality or collecting tradition. These associations vary between sources and are cultural interpretations, not mineralogical or medical properties.
