Patent Number: 043404430
Section: summary

The present invention relates to the determination of the gold content of auriferous materials, and in particular to the determination of the gold content of auriferous rock samples. Gold may occur at depth in thin bands of mineralisation which when mined together are accompanied by substantial quantities of barren rock. In order to prevent the expensive and time consuming treatment of all mined material, it is necessary that some pre-selection process be applied to the mined material. A number of methods of selecting rocks for processing have been proposed but to date no entirely satisfactory method of selection has been found. Some methods have failed because they are secondary methods and the correlation between the secondary property measured and the gold content is either variable or inaccurate; other have not been able to cope with the throughput of samples necessary in a production environment. The present invention provides a method of determining the gold content of mined rock which is both capable of coping with the required throughput of rock samples, and utilises a property of the gold itself to determine its concentration in the rock samples. According to the present invention there is provided a method for determining the gold content of an auriferous material, comprising the operations of irradiating a body of the material with neutrons and determining the intensity of .gamma.-rays having an energy of 279 keV arising from the reaction .sup.197 Au (nn') .sup.197.sbsp.m Au.fwdarw.279 keV. If the method is being used for the determination of the gold content of auriferous rock, then it is necessary to use a neutron source which does not produce neutrons which have an energy above the neutron reaction thresholds of elements such as Al, Si, Ca, Fe and O which are likely to be present in high concentrations. For example, suitable neutron sources are tube sources which utilise the deuteron-deuteron or deuteron-beryllium reaction to produce neutrons.