Abstract
The quantities of magnetic susceptibility or magnetic moment can be used to determine which minerals can be separated from what other minerals by magnetic attraction separation. Now that magnetic rotation separation has been shown to be both possible and practical, there is a need for a practical quantity to describe relative mineral rotation strengths.Such "rotation strength" quantities already exist in mineral physics, in forms such as magnetocrystalline and shape anisotropy constants (or fields). Although these quantities can be used as a guide to mineral particle rotational response to a rotating magnetic field, they are not simple to understand or easy and cheap to measure for very small individual particles, and do not include the effects of other dynamic magnetisation factors such as domain wall velocities. Nor do they include particle inertia and particle shape effects that are of practical concern in a magnetic rotation separation.A practical quantity, the rotation index, can be defined in such a way that it includes all of the above factors and more accurately predicts particle response in a magnetic rotation separator. The rotation index is easily measured on individual particles as small as 50 Ixm, with the same equipment used for magnetic rotation separation.Measurements of rotation index on a population of particles can reveal much about the ferromagnetic structures within the particles, and, used with measurements of magnetic susceptibility, can predict the results of combinations of attraction and rotation magnetic separations.