DAWSONITE

    Class : Carbonates, nitrates, borates
    Subclass : Anhydrous carbonates
    Crystal system : Orthorhombic
    Chemistry : NaAlCO3(OH)2
    Rarity : Uncommon

Dawsonite is a rare sodium aluminum carbonate. It is a secondary hydrothermal mineral that forms at low temperatures by decomposition of aluminum silicates. It was named in honor of the Canadian geologist Sir John William Dawson. Dawsonite forms small lamellar to acicular crystals, colorless or white, exceptionally pink grouped in aesthetic spherolites, tufts, or fine radiated encrustations. The size of the spherolites does not exceed 1 mm.

Main photo : Dawsonite from Francon quarry, Montreal, Canada © Stephan Wolfsried

Dawsonite from Tolfa Mts, Lazio, Italy © Luigi Mattei
Dawsonite from Slaný, Kladno District, Czech Republic © Bohuslav Bures
Pink dawsonite from Limoncino, Tuscany, Italy © Enrico Bonacina
Dawsonite from Poudrette quarry, Mont St-Hilaire, Canada © Gianfranco Ciccolini

Dawsonite in the World

The best dawsonite crystals come from Montreal : they were discovered in fine encrustations on feldspathic dykes cutting limestones near the site of the University of McGill. Dawsonite is also known in several localities in Italy : Livorno, Pian Castagnaio and Santa Fiora (Tuscany), Alpe di Siusi (Trentino-Alto Adige). It is also known from a barite deposit in Algeria, near Ténès, and in Germany.

Dawsonite in France

Davyne is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3
Density : 2.43
Fracture : Undetermined
Streak : White

TP : Transparent
RI : 1.466 to 1.596
Birefringence : 0.130
Optical character : Biaxial -
Pleochroism : None
Fluorescence : White

Solubility : Acids


Magnetism : None
Radioactivity : None

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