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Dawsonite from Mont Saint-Hilaire, Rouville RCM, Montérégie, Québec, Canada
Category Carbonate minerals
(repeating unit)
Strunz classification 5.BB.10
Dana classification 16a.03.08.01
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Imam
Formula mass 144.00 g/mol
Color white
Crystal habit encrustations or radial
Cleavage perfect on {110}
Fracture uneven
Mohs scale hardness 3
Luster vitreous
Streak white
Diaphaneity transparent
Specific gravity 2.436
Refractive index nα = 1.466
nβ = 1.542
nγ = 1.596
Birefringence δ = 0.130
2V angle 77°
References [1][2]

Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO3(OH)2. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath Museum in a feldspathic dike on the campus of McGill University on the Island of Montreal, Canada.[1] It is named after geologist Sir John William Dawson (1820–1899).[2]

The type material is preserved in the collection of the Redpath Museum.[1]

See also[edit]


  1. ^ a b c Dawsonite, MinDat.org, retrieved 2009-12-06 .
  2. ^ a b Dawsonite, WebMineral.com, retrieved 2009-12-06 .