Studies on Ajjanahalli gold ore

Ajjanahalli gold ore deposit is a banded iron formation exposed on a hill containing an average of 2 ppm gold. With a view to establish a viable flow sheet to extract gold from this ore, basic studies on this ore were carried out. Microscopic examination has revealed the occurrence of native gold as tiny occluded grains (<15 microns) in arsenopyrite, pyrrhotite and silicates. Laboratory flotation tests with known reagents have given a recovery of only 57%, indicating that not all the gold is present in sulphides. Direct cyanide leaching of the ore has given about 95% recovery in 24 hrs. Gravity concentration using conventional blankets and tables may not yield good recoveries as the gold is fine grained and partly occluded in sulphides. Hence, a proposal has been made. to crush and grind the ore and treat it directly by cyanidation to recover the gold. Bond's work Index was determined and found to be 12.66 kwh/short ton.