Dawsonite is a mineral composed of sodium carbonate , 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 Island of Montreal Sir John William Dawson
The type material is preserved in the collection of the Redpath Museum.