| Gravity-Recoverable-Gold (GRG) is defined as gold present in a particle in sufficient quantities as to be selectively recoverable from gangue via gravity methods. The McGill standard GRG test is an ore characterization test using three stages of sequential liberation and recovery with a Knelson KC-MD3 centrifuge to determine the size distribution of GRG. This thesis describes the development and testing of two simplified versions of the GRG test, using two and one stages of recovery respectively. Both tests use a feed mass of 20 kg, as opposed to the 40 to 100 kg normally used for the standard test. Eighteen differing ore samples were processed with the simplified GRG tests. For non-abrasive ores the one-stage simplified test returns a similar GRG content and size distribution, making the two-stage test superfluous. For abrasive ores, the one-stage test returns a GRG content that can be as much as 33% relative lower than that of the standard test, with a much finer size distribution. The two-stage test exhibited similar poor performance, though to a slightly lesser degree due to and additional stage of recovery attempted prior to grinding the abrasive material. The GRG lost typically reports to size fractions coarser than 25 &mgr;m, strongly suggesting smearing onto gangue particles. Because of the lower feed mass used, both simple tests are susceptible to the nugget effect; feed representativity also becomes challenging for ore samples of a head grade of 1 g/t or less. |
