13 - Magnetic and electrical separation

Abstract

This chapter explains magnetic and electrical separators, their designs, and types. Magnetic separators exploit the difference in magnetic properties among the ore minerals and are used to separate either valuable minerals from non-magnetic gangue, for example, magnetite from quartz, or magnetic contaminants, or other valuable minerals from the non-magnetic values. An example of this is the tin-beating mineral cassiterite, which is often associated with traces of magnetite or wolframite that can be removed by magnetic separators. Magnetic separators can be classified into low and high-intensity machines, which may be further classified into dry-feed and wet-feed separators. Low-intensity separators are used to treat ferromagnetic materials and some highly paramagnetic minerals. Electrical separation utilizes the difference in electrical conductivity among the various minerals in the ore feed. Since almost all minerals show some difference in conductivity, it would appear to represent the universal concentrating method. In practice, however, the method has fairly limited application, and its greatest use is in separating some of the minerals found in heavy sands from beach or stream placers.