4.1.2 Roasting and Smelting

In metal mines, heat is used to continue the process of concentrating the iron, copper and gold metals and eliminate any impurities.

The principles are age-old and involve a fuel and air introduced with bellows.

		Cross-section of a blast furnace, circa 1750.
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In Quebec, the Forges du Saint-Maurice (1735-1883) are the finest example of ancient ironworks which reduced iron ore and flux in furnaces heated with charcoal.

		Blast furnace complex at the Forges du Saint-Maurice, 1880.
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Copper smelting in the 19^th century in Quebec was first practiced at the Eustis mine (1865-1939) using small-scale methods: roasting in open-air furnaces to burn off most of the sulphur , followed by smelting to increase the copper content (between 40% and 70%); the copper was then shipped in the form of matte to the United States.

In operation since 1927, the Noranda smelter became the prototype for copper smelters. The concentrates, together with the flux and non-concentrated ore, are roasted in furnaces fuelled by the sulphur oxide in the ore and by coal.

		Noranda smelter, 1934.
	Source

The copper is concentrated further in reverberatory furnaces, producing a matte that is ready for converting.

In gold mines such as the Lamaque mine, furnaces, more modest in comparison, cast the gold in gold bars ranging from 80% to 90% in purity, which are then shipped to the Royal Canadian Mint in Ottawa to be refined to a purity of almost 100%.