TABLE OF CONTENTS Magnetic and electrical separators are being considered in the same chapter, as there is often a possibility of an overlap in the application of the two processes. For example, as can be seen later, there is often debate as to which form of separation is best suited at various stages to the treatment of heavy mineral sand deposits.
Magnetic separators exploit the difference in magnetic properties between the ore minerals and are used to separate either valuable minerals from non-magnetic gangue, e.g. magnetite from quartz, or magnetic contaminants or other valuable minerals from the non-magnetic values. An example of this is the tin-bearing mineral cassiterite, which is often associated with traces of magnetite or wolframite which can be removed by magnetic separators.
All materials are affected in some way when placed in a magnetic field, although with most substances the effect is too slight to be detected. Materials can be classified into two broad groups, according to whether they are attracted or repelled by a magnet:
Diamagnetics are repelled along the lines of magnetic force to a point where the field intensity is smaller. The forces involved here are very small and diamagnetic substances cannot be concentrated magnetically.
Paramagnetics are attracted along the lines of magnetic force to points of greater field intensity. Paramagnetic materials can be concentrated in high-intensity magnetic separators. Examples of paramagnetics which are separated in commercial magnetic separators are ilmenite (FeTiO 3), rutile (TiO 2), wolframite ((Fe,...
