Sorting diamond bearing ore

摘要

In order to sort diamond-bearing ore particles 2 conveyed on a wide belt 1, exciting radiation strikes the belt along an extended line. Diamonds are detected by passing the emitted radiation through a narrow band pass filter 9 and sensing the Raman radiation with a photo-multiplier tube 14. Only nearby axial-parallel rays passing through the filter reach the photo-multiplier tube. An array of side-by-side rectangular converging lenses 15 can be used, the ore particles being in the plane of the foci of the lenses. To stop rays having an angle of incidence greater than the maximum permitted, to avoid identifying non-diamond material as diamond, a further converging lens 10 is used to focus the rays at the plane of a telecentric stop 11. The position of the diamond can be detected for instance by a CCD array or by a time domain technique. The calibration of the apparatus can be monitored by detecting when the radiation from reference stones and holes on either side of the belt differs from predetermined values.