A plant was commissioned and optimised to produce an average gold recovery of 98% at 80% passing 106 m but lately the recovery has dropped to 85%. To identify the route cause, samples were taken from the Ball mill discharge and leach tails. Sieve analysis was performed on the Ball mill discharge and size by size deportment on the leach tails. Summary of results are presented in the Tables 1. i. Develop a screen analysis table showing the cumulative percentages passing and estimate the d80 value for the ball mill discharge using interpolation ii. Perform a gold deportment analysis for the leach tails sample and estimate the calculated head grade for the leach tails. iii. What is the percentage and grade of leach tails material reporting to -106 m? iv. What could be the possible cause for the drop in gold recovery?

A plant was commissioned and optimised to produce an average gold recovery of 98% at 80% passing 106m but lately the recovery has dropped to 85%. To identify the route cause, samples were taken from the Ball mill discharge and leach tails. Sieve analysis was performed on the Ball mill discharge and size by size deportment on the leach tails. Summary of results are presented in the Tables 1. i. Develop a screen analysis table showing the cumulative percentages passing and estimate the d80 value for the ball mill discharge using interpolation (10 marks) ii. Perform a gold deportment analysis for the leach tails sample and estimate the calculated head grade for the leach tails. (10 marks) iii. What is the percentage and grade of leach tails material reporting to -106 m ? (6 marks) iv. What could be the possible cause for the drop in gold recovery? (10 marks) \begin{tabular}{|c|c|c|c|c|} \hline Sieve(m) & Mass retained (g) & Assay(g/t) & Sievesizerange(m) & Mass retained (g) \\ \hline \multicolumn{4}{|c|}{ Leach tails } & \multicolumn{2}{|c|}{ Ball mill discharge } \\ \hline+300 & 1019.4 & 2.86 & +180 & 8.0 \\ \hline300+212 & 80.20 & 6.98 & 180+125 & 11.2 \\ \hline212+150 & 61.80 & 15.92 & 125+90 & 12.8 \\ \hline150+106 & 57.00 & 14.44 & 90+63 & 14.4 \\ \hline106+75 & 35.40 & 17.94 & 63+45 & 16.0 \\ \hline75+38 & 95.10 & 12.08 & -45 & 17.6 \\ \hline-38 & 651.10 & 13.98 & & \\ \hline \end{tabular}