Gravity Concentration at W.M.C.'s ST.IVES Gold Mines

Barry Cloutt
Presented at the Randol Gold Forum, March 1995 Perth W.A .

December 17th, 1998

St. Ives Gold Plant is located near Kambalda, approximately 90 kilometers south of Kalgoorlie in Western Australia.

Three Knelson Concentrators were located on the level below the pre-concentration screen and above the two ball mills. Five objectives were applied to justify a Knelson Concentrator gravity recovery system:

1. Reduced costs due to a reduction in the amount of carbon needed to be stripped.
2. Increase in revenue due to improved recoveries.
3. Cost savings due to a reduction in cyanide usage in the CIP plant.
4. Improved adsorption kinetics.
5. A reduction in the amount of gold locked up in the circuit and losses due to tailings spikes.

The commissioning of the plant has in the main met all of the objectives that were set out in the initial justification over 12 months previously.

Savings: The savings in the elution plant were estimated by comparing the relative amount of gold recovered over an extended period. This then equated to a saving of 107 strips or 30.3% of the total stripping costs annualized at a savings of $400,000. A reduction in cyanide usage was recorded at 0.121 kg/t and an annual cost saving of over $350,000. The performance of the adsorption section of the CIP plant has met or surpassed all expectations. A decrease in the solution tailings represents a 28% reduction in gold lost in the solution phase alone.

The annual increase in revenue since the commissioning of the gravity circuit is therefore approximately $1.272 million at an average gold price of A$515/oz and an approximate payback period of the project was seven months.

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