Concentration of Gold

Concentration: Concentration or pre-concentration as it is often called because of its position ahead of cyanidation in many gold extraction flowsheets, can be use to upgrade ores to:

Produce a high grade gold concentrate in a small weight fraction of the feed for more economical subsequent treatment.

Reject a portion of the ore that contains no gold to reduce the bulk of feed to subsequent processes.

Reject a portion of the ore that is barren but which otherwise adversely affect subsequent gold extraction, e.g. cyanide consumption sulphides, gold absorbing carbonaceous matter and acid consuming carbonates.

The economic incentive for concentration is that the cost saving achieve by treating a smaller amount of material, or by removing deleterious material, is greater than the loss of valuable mineral in the rejected portion. The upgraded fraction is then treated further by various processes, depending on the grade, quantity, mineralogy and metallurgical properties.

Ore sorting is the rejection of a barren portion of ore or the acceptance of a gold rich portion for further treatment. This can be achieved by manual sorting based on the visual appearance of the material, or with mechanized ore sorting equipment, that rely on bulk ore properties such as optical appearance or radioactivity. Ore sorting has been applied with considerable success to the Witwatersrand pebble-quartz conglomerate ores in South Africa.