Carbonaceous ores

C arbonaceous ores are those containing components which absorb dissolved gold during leaching thereby reducing gold extractions by cyanidation. These gold ores sometimes require pretreatment prior cyanidation. Important examples are Ashanti and Prestea (both in Ghana) and Carlin (Nevada, USA).

Carbonaceous matter is also present in Witwatersrand ores (sometimes called Thucholite) though it contributes only a small extent to reduced gold extraction. The term Thucholite is derived from the elements present, i.e. Th, U, C, H, O (-lite) and generally describe radioactive hydrocarbon.

Carbonaceous matter can absorb gold from solutions. Although this material generally does not have as high specific surface as activated carbon, in some ores the high iron content result in a significant reduction in gold extraction. In some cases as little as 0.1% carbon can cause pre-robbing properties. Such carbonaceous matter consists of hydrocarbon, humic acid and elemental carbon.