How does magnetic separation remove magnetic minerals from gangue?

Magnetic separation is a process used in metallurgy to isolate valuable minerals from gangue based on the varying degrees of attraction minerals exhibit when exposed to magnetic fields.1

The effectiveness of this method depends on the magnetic susceptibility of the minerals and the intensity of the magnetic field applied:

• Low-intensity magnetic separators: These are used to remove strongly magnetic minerals, such as magnetite, franklinite, and pyrrhotite, from non-magnetic gangue.1
• High-intensity devices: These are required to separate weakly magnetic minerals, including oxide iron ores like limonite and siderite, as well as iron-bearing silicates and ores of manganese, titanium, and tungsten.1

For the process to be successful, the feed particles must typically fall within a specific size range, generally between 0.1 and 1 millimetre. Beyond its primary use in ore concentration, magnetic separation is also employed to recover and recycle heavy media—such as magnetite or ferrosilicon—used in gravity-based sink-and-float separation processes.12