Auriferous deposits worldwide are present into three types: vein deposit (5%), placer (70%) and associated gold deposit (25%). The early gold exploitation focused on placer and later turned to vein deposit, which now accounts for 65% of total gold production.

Pretreatment of gold ore had been taken seriously because it contributes a lot to the extraction. Once the ore is mined, the raw ore is firstly crushed and milled to expose auriferous minerals (mainly native metal). Before leaching, the grain size is prepared to 0.4mm, 74μm or 44μm depending on the leaching test result. In case the raw ore is highly oxidized or of too much slurry, hydrocyclone and thickener are used to remove slurry. Gravity separation or flotation may be used to concentrate gold.

Gold minerals is usually treated by cyanide leaching process including heap cyanide leaching, CIP (carbon in pulp), RIP (resin in pulp) and CIL (carbon in leaching). Those gold ore whose leaching rate is less than 80% by conventional cyanide leaching even for 20-30 hours is considered as refractory gold ore. Metalcess develops high temperature chloride leaching technology, especially to deal with refractory gold ore.