Characterisation of Gravity Amenable Gold Ores – Sample Representivity and Determination Methods

摘要

Gravity amenable gold ores are those that after comminution produce liberated particles,rncomposites and/or carriers that can be recovered by gravity separation means. Recovery dependsrnupon mineralisation type and the comminution and concentration method used. Any in situ orernwith more than 20 per cent of gold greater than 100 μm in size is likely to have a strong gravityrnrecoverable component. A less traditional approach is where the gold is sulfi de-locked and the goldrncarrier plus any liberated gold is recovered via continuous gravity recovery following fi ne crushing.rnSpecifi c tests are undertaken to determine the level of gravity amenable gold within a deposit.rnThe principal methodology is the gravity recoverable gold (GRG) test, which consists of threernsequential liberation and recovery stages. For continuous gravity recovery (CGR), the sample isrnfed over a laboratory Wilfl ey table to simulate continuous recovery of the gold. Tails from the feedrncan be progressively re-ground and re-tabled to develop a grade-recovery curve. Primary geologyrnand gold particle size-distribution have a strong effect on the mass of sample required to providernrepresentative results for both tests. Where low-grade ore contains very coarse gold, substantiallyrnlarger sample masses are required. Experience has shown that GRG and CGR values can varyrnthroughout an orebody, particularly within different geological-grade domains. A testing regimernmust consider sample frequency and support.