Dissatisfied with conventional wet processing methods for alluvial
deposits, Resource Trend Pty Ltd of Cairns set out to develop a better
process. After comprehensive investigation of existing dry techniques the
principals have now developed a rotary dry concentrator that can handle
the fine-grained fraction of alluvial deposits as well as the coarse. Four of
these units have been mounted on an integrated towable treatment plant
which has been in successful commercial operation for four years in
northern Queensland. A second plant is now under construction for use in
the United States. Grades of less than 0.2 g/lcm have been profitably
mined at throughputs of about 80 cubic metres per hour and 85 per cent
availability. The operation runs round the clock with an establishment of
four. Major benefits, apart from lower capital and operating costs, are
environmental. Ore is picked up, treated, and replaced in its original
mixed condition within 25 m of its initial location. Rehabilitation is
completed almost immediately behind the plant as it advances, leaving no
slimes dams, coarse stockpiles, or haul roads. In 1993 the company won
a Premier's Award for Environmental Excellence in the Queensland
Mining Industry. The principal disadvantage is moisture, and the company is now
actively seeking deposits in the deserts of the world. In Queensland
mining is normally possible only for six months of the year.