State Research Institute of Nuclear Geophysics and Geochemistry, and Central Mining and Prospecting Research Institute of Non-Ferrous, Rare and Noble Metals of the Ministry of Geology of the USSR Moscow USSR
The difficulties of determining gold in rocks and ores are due to two causes: low gold concentrations in rocks (Clark 1 to
4·10−7%), and non-uniform distribution of gold in ores. A method is proposed which is based on neutron activation of the lead alloy
obtained by cupel melting in the procedure of determining gold by cupel assay. Samples of 50 to 100 g are used for cupel melting.
Such large samples guarantee their representativeness. Discs of 2 to 3 g are cut from the lead alloy block and activated in
a neutron flux of 1011 to 1013 n·cm−2 sec−1. The gold content is determined from the photopeak of198Au using a standard for comparison. The sensitivity of the method is 0.02 g/metric ton, its accuracy at a gold content in
the order of 1.0 g/metric ton is 10% relative. The method is distinguished by the fact that it is fast and requires little