GB1384813A - Separation of diamonds by electromagnetic radiation - Google Patents

Abstract

1384813 Uses of luminescence DE BEERS CONSOLIDATED MINES Ltd 10 Feb 1972 [12 Feb 1971] 6296/72 Heading C4S [Also in Division G1] Diamonds are sorted from a mixture by irradiating the mixture, detecting luminescence therefrom and dividing the diamonds into fractions in accordance with different spectral characteristics. The radiation may be γ-rays from a Co 60 source, X-rays from an X-ray tube or ultra violet radiation from a lamp which may require a u.v. filter. A grating spectrometer provided with a choice of photomultipliers to cover the full spectral range, or a plurality of filters, may be used for the spectral analysis. Characteristics which may be used in combination may be the unique spectra of the different types of diamonds and common impurities (spectral signatures), ratios of different parts of the spectra or decay characteristics. A compressed air blast sorter may be used on a single particle stream on a conveyer belt or freely falling. Various examples of luminescence characteristic spectra are provided (not shown) for four types of diamond, zircon and fluorite, at room and liquid nitrogen temperatures.