Natural Phenomenon: Rosebery Lead-Zinc-Gold-Silver-Copper Deposit
Summary
The Rosebery Lead-Zinc-Gold-Silver-Copper Deposit is a massive strata-bound sulphide orebody associated with silicic pyroclastic and sedimentary rocks of the Cambrian age Mount Read Volcanics, the same rocks in which the Hercules, Que River, Hellyer, Henty and Mount Lyell sulphide deposits are found.
Details
The first mineral discovery in the Rosebery area was a tourmaline lode in 1890, thought to be a silver deposit, but it came to nothing. The Rosebery orebody was discovered by Tom McDonald, who found alluvial gold and boulders of zinc-lead sulphide in a creek on the slopes of Mount Black. The Rosebery Prospecting Association, under McDonald's supervision, then discovered a zinc-lead sulphide orebody in a deep trench. A number of smaller mines were opened, but metallurgical difficulties in separating sphalerite (zinc) from galena (lead) led to their closure by 1900. Operations resumed in 1905, the ore being railed to the Zeehan Smelters for treatments. The smelters closed in 1913. The Electrolytic Zinc Company of Australia acquired the mine in the 1920s to provide ore for its refinery at Risdon, and the mine still provides 40 percent of the feed for the refinery. At first mining depended on shaft access and hoisting, and rail transport. Modernisation has resulted in the introduction of trackless diesel operations. After a decline was made from the surface to producing areas, shaft operations were discontinued in 2003.
After a century of operation, the mine has yielded copper, gold, lead, zinc and silver from more than 18 million tonnes of ore. With an estimated metal value of $8 billion, Rosebery has produced more wealth than any other mine on Tasmania's west coast.
Carol Bacon, Greg Dickens and Wojciech Grun