Abstract:
The Humphreys Spiral Concentrator which was developed in 1943 is now being used
extensively for the concentration and the recovery of heavy minerals. In Sri Lanka,
this device is very effectively used by the mineral sand industry and in the
beneficiation of glass sands. The advantage of this over the Wilfley Table is that the
capacity of Spirals are high and the running costs are very low.
The study conducted by the author has shown that this method can be profitably used
in the upgrading of Gold bearing sands. In this study, samples of river sands collected
from Welioya, Kaltota area were subjected to gravity separation using the Spiral
followed by the Wilfley Table. The concentrates obtained by this research showed
Gold values ranging from zero to 0.0019%.
The discovery of Cyanide heap leaching followed by activated Carbon Adsorption
now makes it possible for samples containing considerably less than 0.0003% to be
considered an ore. Thus, the beneficiated samples have economically recoverable
Gold values.
