On 9 April 1940 Germany invaded Demark. Instantly the fate of Greenland, a Danish colony, was thrust into limbo. The Aluminium Company of Canada (Alcan) had particularly self-interested concerns in the future of the island. In 1940, Greenland was home to the world’s only working mine and known major deposit of natural cryolite, a mineral essential to the aluminium smelting process. The Danish had been in control of cryolite mining and refining since its initial commercial development and a German-occupied Denmark posed a major threat to the global cryolite supply. This paper discusses the ways in which cryolite and the Canadian aluminium industry influenced Canada’s role in the genesis of the American occupation of Greenland and considers lessons that can be gleaned from the past for contemporary Greenlandic industry and society.