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Gold ores in Tasikmalaya region, West Java, are commonly found in the form of sulfide ores. Sulfide minerals generally include chalcopyrite, pyrite, galena, sphalerite, and chalcocite. These sulfide minerals would obstruct the extraction of gold through cyanidation process. According to XRF test, it is obtained that Tasikmalaya ores contain 83.68% of silica. Cyanidation of gold was carried out in three conditions. The first condition was done by roasting the gold ores before cyanidation. The second one was conducted by adding H2O2 and the last one by doing cyanidation process without roasting and H2O2 addition. The cyanidation process was carried out along 48 hours with cyanide concentrations varied of 300, 500, and 700 ppm. The highest gold recovery of 95.86% was achieved through H2O2 addition with 700 ppm of cyanide concentration. [ABSTRACT FROM AUTHOR]

In the processing of nickel ore into ferronickel, simultaneously dust is produced in the rotary dryer, rotary kiln and electric furnace. The dust still contains nickel. Dust is formed into pellets and will be reused in rotary kiln for ferronickel production. Ferronickel dust pellet is processed by reduction through addition of coal as much as 10% of pellet weight with a variation of reduction temperature at 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, and 1400 ℃ to observe growth of ferronickel particles. Study of reduction of composite pellets, pellet of ferronickel plant dust was mixed with coal reductor as much as 10% of their weight and then reduced at temperature of 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, and 1400 ℃ for 30 minutes. Reduction behavior of pellet can be analyzed with XRD and analysis of particle growth of ferronickel was observed by using optical microscope. At this temperature SiO2 reduced to Si and reacts with Fe to form Fe3Si. The length of ferronickel particles increases along with increase of temperature. At a temperature of 1000℃ = 43μm, 1100 ℃ = 152 μm, 1200 ℃ = 419 μm, 1300 ℃ = 736 μm, and 1400 ℃ = 1426 μm. Increasing ferronickel particles showed that particle growth occurs on increasing the temperature. [ABSTRACT FROM AUTHOR]