Technical Report for the Fort Knox Mine - Kinross Gold

Fort Knox Mine Technical Report16.1.2 Mill Recovery – Fort Knox DepositGold recoveries at the Fort Knox mill have historically ranged from 87 percent to morethan 90 percent since production began in 1996. During 2001 to 2004 it was necessaryto add lead nitrate and slightly increase the cyanide and lime concentrations to maintainmill recovery rates with some of the feed coming from True North.The historical production at Fort Knox allows a gold grade to recovery relationship to bedeveloped. Table 16-1 summarizes this relationship for the Fort Knox mine based onseveral years of production experience. At the $550 per ounce A-ore, cutoff grade(0.0150 oz Au/short ton) the predicted recovery is 88.25 percent, while for the averagegrade for reserves scheduled to be milled (0.0225 oz Au/short ton) the predictedrecovery is 89.36 percent.Table 16-1: Grade Recovery Relationship - Fort Knox MineGrade oz/ton 0.010 0.015 0.020 0.025 0.030 0.035Recovery 86.82% 88.25% 89.31% 90.16% 90.85% 91.5%Grade oz/ton 0.040 0.045 0.050 0.055 0.060Recovery 91.97% 92.43% 92.85% 93.23% 93.57%16.1.3 Mill Recovery – True North DepositThe True North mineral model has both a fire assay grade for in situ reserves andresources and a cyanide soluble (CN) grade for the estimation of recoverable gold. Thecutoff grade and daily grade control are based on the cyanide soluble grade. A monthlycomparison between the predicted CN grades in the mineralization model and the backcalculatedhead grade from the mill indicated that a 96 percent recovery factor isrequired to estimate the True North gold produced from 2001 to 2004. True North ore isnot currently being processed at Fort Knox.49