Separation of gold and other rare materials from an ensemble of heterogeneous particles using a NdFeB magnetic circuit.

Most solid particles, composed of diamagnetic or weak paramagnetic materials, cannot be extracted by a conventional magnetic separator. Here we report that an ensemble of heterogeneous particles, composed of bismuth, gold, graphite and rock forming minerals are separated into fractions of different materials by small NdFeB magnetic plates. It is based on a recent finding that acceleration of a translating particle, induced by magnetic volume force in an area of field gradient, is uniquely determined by intrinsic susceptibility of material; the acceleration is independent to particle mass. The setup will serve as an effective technique of pre-treatment in analysing mixture of heterogeneous particles; such a technique is desired in various research fields of science, and the magnetic separation may play a role of a "chromatography technique" conventionally used in the analysis of organic molecules. The portable and low-cost system could provide a breakthrough for on-site research in industrial and medical fields as well as in resource explorations in nature. Extraction of rare materials such as gold or platinum becomes possible in a hazardless manner.