3.4.2 Milling

At the surface, the rock was crushed in stages to obtain increasingly fine granules and particles.

Soon metal or stone stamps were introduced and used for many years.

		Washery and stamp mill, 1750.
	Source

For copper and gold, chemical processing by flotation in cells males it necessary to reduce the ore to dust. Milling is therefore an essential stage in ore concentration.

		Ore crusher, Noranda mine, 1934.
	Source

		Crushed ore sieve, Noranda mine, 1934.
	Source

Crushing methods generally involve the use of mechanical or gyratory crushers. Centrifugal force and the collision of fragments in the enormous rotating drums, called "cyclones" in asbestos milling, do the job.

For copper and gold, successive flotations in chemical solutions followed by filtration produce concentrates that are ready to be subjected to the heat of the furnaces. This operation extracts the iron and some of the gold from the ore.

		Flotation cell, Noranda mine, 1934.
	Source

Most of the mines in Northwest Quebec concentrate the ore on site and then ship it to a regional smelter such as the Noranda smelter, which opened in 1927.