Development of a standard operating procedure for determination of gold grade in ore and tailings for artisanal, and small-scale gold miners.

Abstract

Determination of gold grade prior to mining investment helps to understand and determine the possible expenses and cash flows from the project. With the ore grade and commodity price in the market, the project proponents (investors) are able to make the rightful investment decisions. Several techniques and tools are employed worldwide to carry out this analysis. A study was carried out to develop a standard procedure by (l) qualitatively analyzing the metal composition in the ore, (2) quantifying the ore, (3) validating the ore quantification and (4) carrying out an economic analysis for the developed procedure. Samples were obtained from around the Tira Gold Field and thoroughly prepared to ensure that the results are unbiased. The qualitative analysis showed that the metal composition in the ore was not significant enough to show presence after pre-leaching and ore opening using sulphuric acid but showed significance during the leaching process witnessed by excessive consumption of cyanide. The quantified ore grade was far higher than the actual grade as determined from the AAS. Validation was carried out to ensure that the higher values obtained from quantification be accounted for and this was done using excel spreadsheet. An economic analysis was carried out too to ascertain the economic viability of the new procedure as compared to the other existing methods. The results showed that this procedure was 6.8727 times cheaper than the use of the AAS machine and analyzing samples at different laboratories at Makerere University and the Department of Geological Survey and Mines. The research recommended that further and more detailed ore opening be carried out to ensure that all the metal ions are completely dissolved into the solution and measures be taken to eliminate or suppress their significance on cyanide consumption to minimize on the costs involved in purchasing cyanide. A simplified approach was given that can be used by the local artisanal miners to apply the procedure without much technical challenges involved in carrying out the mole concept.