High gradient magnetic separation applied to tin minerals

The present work reports the application of wet High Gradient Magnetic Separation, HGMS, to the recovery of weakly paramagnetic particles of very small dimensions. Pure minerals of different iron content were recovered magnetically with applied magnetic field intensities of up to 19 kOe under various conditions of flow velocity and separating matrix density. Tourmaline mineral, the main impurity in tin ore, can be recovered with a maximum of 63% efficiency in a single passing of HGMS at maximum field and 6 cm/sec flow velocity whereas cassiterite mineral (SnO2) from the same ore deposit and particle size can be recovered with 37% efficiency. With a second passing of HGMS tourmaline was recovered with an increase of 14% in efficiency. From these results it seems possible that one could separate tourmaline minerals from cassiterite minerals with the appropriate conditions of magnetic field intensity, flow velocity and separating matrix density.