Commissioned in 2004, Kalana is founded on a rich quartz-vein orebody, and mill feed ore typically grades between 8 and 15 g/tAu. The vast proportion of the gold is gravity recoverable, and rather than becoming mired in complex cyanide leach technology, Somika MD Roy Meade decided on a gravity-only recovery circuit, and selected  Knelson as the preferred supplier.

The Knelson treats the entire ball mill discharge stream after screening; Knelson tails and re-ground screen overflow is fed to the mill hydrocyclone and cyclone overflow is pumped to tails without further treatment. Recently a second-hand 1994 model Knelson KC-MD20 was incorporated on the cyclone overflow, but it recovers only a few ounces of gold per month. About 99% of the recovered gold is attributable to the primary KC-CD30 concentrator.

"Plant recovery averaged 87% for the period July '08-July '09 and continues to lie in this range", said Somika MD Roy Meade. "No unusually fine grinding is employed, and no extra effort is put into gravity recovery over and above the norm for a Knelson within the circulating load. Gravity recovery has exceeded the mine design of 79% for a head grade of 14g/t, even when the head grade fell to 10g/t. Recovery was 92% with a head grade of 25g/t in 2007."

In a typical month the Knelson recovers about 1500oz of gold, valued at 15 times the price of the machine, and yet its operating costs are practically zero. Since commissioning in 2004, Somika has replaced only 1 concentrate cone, 3 bearings and 1 rotary union.

Roy’s choice of Knelson has certainly paid dividends.