Small scale mineral processing practices are regarded as crude and wasteful process, thus, the tailings produced from their operations still contain substantial amount of gold due to the inefficiency of the process. Reprocessing of these tailings is feasible due to the significant amount of gold left in the tailings. Mining and milling were already undertaken previously, thus, processing cost is also reduced.

The metallurgical investigation conducted involves wet screening to determine the particle size distribution of the small-scale gold tailings; gravity separation to verify if there are still free/coarse gold left; flotation to collect most of the gold with minimal weight of flotation concentrate; roasting of flotation concentrates, and gold leaching (cyanidation). The equipment used were set of standard screens, shaking table, flotation machine, rotary kiln and bottle roller for cyanidation. The gold content was determined by Fire Assay.

Initial results of metallurgical tests showed a recovery of above 82% but with a concentrate yield of above 35%. A consistent gold recovery of 58% on the flotation tests was obtained on the later part of the study with a concentrate yield of less than 7%.

Inventory of small-scale gold tailings should be conducted to evaluate and obtain a close estimate of the mineral resource available and to determine the average head grades per tailings pond. Additional optimization tests of flotation reagents using environment friendly di-thiophosphate collectors in combination with suitable co-collectors must be conducted. Moreover, confirmatory straight cyanidation bottle roll tests must also be undertaken for roasted and unroasted flotation concentrates.

Bernardo V. Bitanga and Rey V. Perucho
Metallurgical Technology Division
Mineral Processing Research and Development Section