Dumortierite

An interesting blue or purple mineral which occurs in a fibrous state.

This stone occurs around the world, in a range of countries. It is an aluminium based borosilicate, similar to Kyanite – both of which are blue and used in the production of ceramics.

In some cases, it occurs as inclusions in Quartz, which are absolutely gorgeous!

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Appearance, Uses and History

This stone occurs around the world, in a range of countries. It is an aluminium based boro silicate, similar to Kyanite – which is also blue, and also used in the manufacture of ceramics.

It was named after Eugene Dumortier, a 19th century French palaentologist.

It has been sold by less scrupulous sellers as Sodalite or Lapis Lazuli – and it is understandable how the untrained eye could be mistaken, when the stone is polished. Even the larger crystal structures of the stone could be mistaken if the colour is right.

It is sometimes referred to as ‘Dumortierite Quartz’, but this is an inaccurate name. Dumortierite Quartz specifically refers to pieces of Quartz with inclusions of Dumortierite. These pieces are quite desirable to collectors, as blue Quartz is surprisingly rare, despite the commonness of Quartz itself.

Dark blue pieces are the most common – usually with patches of other colours, light blue or grey being the second most common.

It is a hard mineral and can be cut for jewellery – although limited knowledge of the stone and the rarity of high quality pieces mean cabochons etc can be quite hard to find, with faceted stones being even rarer.


Locales

Austria, Brazil, Canada, France, Italy, Madagascar, Namibia, Nevada, Norway, Peru, Poland, Russia and Sri Lanka.


Mineralogy

Chemistry
An Aluminium borosilicate, with the chemical formula AlAl6O3BSi3O18.
Colours and Variations
Typically light to dark blue. Sometimes grey-blue, purple, pink or brown.
Streak
White
Luster
Vitreous, silky, or dull
Fracture
Uneven, splintery, fibrous
Transparency
Translucent to Opaque
Crystal habit
Radiating sprays, fibrous masses, needles, compact masses or granular patches on matrix.
Mohs hardness
7 – 8
Specific Gravity
3.2 – 3.45
Easiest testing method
Sometimes fluorescent.
Common Treatments

Photos of Dumortierite

Dumortieriet 001
Dumortiérite 1
Dumortiérite

Dumortierite-150241

Hazards and Warnings

Dumortierite contains aluminium and is listed online as toxic relatively often. However, aluminium cookware exists – I suspect you’d have to eat powdered Dumortierite for it to be an issue.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis.

When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.


Translations

Arabic:

Hindi:

Portuguese:

  • dumortierita

Bengali:

Indonesian:

Punjabi:

English:

Italian:

Russian:

  • дюмортьерит

French:

  • dumortiérite

Japanese:

  • デュモルティエライト

Spanish:

  • dumortierita

German:

  • Dumortierit

Korean:

Thai:

Gujurati:

Mandarin and Traditional Chinese:

Urdu:


Further Reading / External Links