Historically, the copper, gold and tin booms of the previous decades set precedence for the 1880s were the lead-silver and later zinc in the 1900s in Australia. Majority of Australia’s foremost mining companies were established in the 1880s with the birth of Broken Hill Proprietary Company on 10 August 1885 now known as BHP Billiton in which the Broken Hill field was particularly dominant for silver and zinc mining in Australia. Towards the end of the decade Broken Hill was a world-renowned silver field with increasingly important lead production and at this stage there was no interest in zinc the sole focus was silver grades being mined from oxidized ore in the weathered zone by BHP. The mid-1800s saw minor attempts at mining lead-silver ores such as Glen Osmond near Adelaide in 1841, the Northampton field of central western, Western Australia from 1852, the small Yerranderie and Captain’s Flat fields in eastern New South Wales in the 1870s and the Chillagoe field in the northern Queensland towards the end of the 1870s. In the 1880s, several new fields were discovered at the Thackaringa-Silverton in 1876 but not confirmed until 1880 and Broken Hill in 1883 in far New South Wales, Zeehan of western Tasmania in 1882 and Lawn Hill of north-western Queensland in 1887. A step back into the history of silver and copper mining in Australia is setting a tone for definitions of what silver and zinc are, where they are mined in Australia with examples of recent investments from Australian government and wrapping up with the importance of dust control from a Global Road Technology perspective.
What is silver and how is it found in nature?
Silver is a stable, ductile and malleable transitional element found widely throughout the world. Its name was derived from Anglo-Saxon seolfor or siolfur, and Latin argentum. It is fractionally harder than gold but has the highest thermal and electrical conductivity of all metals. Silver accounts for 0.1 ppm in the Earth’s crust and about 0.3 ppm in soils and occurs as cubic crystals and in deposits of pure metal in the form of two isotopes 107Ag and 109Ag which occur in approximately similar proportions. Silver ores found naturally include sulfide, sulfate, bicarbonate, telluride and complexes with other metals such as lead, zinc, copper, gold, mercury just to mention but a few. In addition to the numerous deposits of pure silver metal, the principal mineral ores of silver include argentite (silver sulfide), proustite (complexed with arsenic and sulfur), stephanite and pyrargyrite (complexed with antimony and sulfur), hessite (complexed with tellurium) and cyrargyrite (silver chloride). Australia is amongst the principal silver mining areas of the world.
What about Zinc?
Zinc was not isolated as a separate metal in ancient times but was always alloyed with copper to give brass dating back to the Roman empire. The alloy was produced by heating with copper granules together with zinc oxide and charcoal. The discovery of vast zinc resources at the Broken Hill field in Australia provided incentive for development of new techniques for differential mineral separation. Owing to the strong affinity for cadmium and mercury to zinc, its mineralization always contains the two elements at varying ratios. The common zinc minerals include sphalerite also known as zinc blende or wurtzite (zinc sulfide), marmatite (iron in solid solution with zinc and sulfur), smithsonite or calamine (zinc oxide, zinc carbonate and water), willemite (zinc oxide and silicon dioxide), hemimorphite (zinc oxide, silicon dioxide and water) and finally zincite (zinc oxide) which contains the most abundant zinc content of about 80.4%. most commercially viable zinc orebodies contain zinc above 4% and rarely above 20% in mass although zones of pure sphalerite can possibly occur and the degree of separation from gangue and other metallic sulfides is governed by both economics and competitive pressures. It is key to minimize the amount of waste materials associated with zinc mineralization so as to reduce the costs of transport of the concentrate from the mine to the smelter hence it is preferable to retain as much waste in mine tailings as possible.
A historical perspective of Silver and zinc mining in Australia
In the 19th century, exploration of zinc in Australia faced many challenges associated with the lack of economic recovery technology and limited market interest relative to silver. In order to improve economic efficiency on the Broken Hill field, the zinc problem had to be resolved which led to the invention of the flotation method with its different variants a technology that was adopted from the British run Zinc Corporation in 1905. In 1916, creation of the Electrolytic Zinc Company of Australasia Ltd (EZ) established a zinc refinery near Hobart in Tasmania. The Zinc Corporation formed the Consolidated Zinc Corporation which merged with UK’s Rio Tinto Zinc to form Conzinc Riotinto Australia Ltd which took over Broken Hill South Silver Mining Company Ltd and North Broken Hill Ltd in 1980 and 2000 respectively. Elsewhere, in 1923 John Campbell Miles discovered the Mt Isa lead-zinc-silver field in northwest Queensland which has very slow potential compared to Broken Hill owing to the remoteness of Mt Isla, the difficult nature of finer graded ores to mill and smelt as well as the easily treatable oxidized ore.
Are environmental regulations, health and safety concerns or potential profit loss a concern right now?
How is silver and zinc mining developing in Australia?
We will now look at the more recent developments in zinc and silver mining in Australia with specific mention of Cannington silver and zinc mine south of Cloncurry which has contributing majorly to the Australian production and stabilizing of ore grades of zinc and silver. Most recently, the Australian government pledged support of up to $11 million for the Copper String project. The investment will boost economic vibrancy of Queensland in lowering prices and creating employment and unlock the vast economic potential of the North West Minerals Province. A decade ago, silver from the Cannington Mine was used for the silver medals for the Sydney Olympics. History does justice to connecting the events that led to the vibrant silver and zinc mining industries in Australia and key to sustainability is the duty to care from companies actively involved to ensure worker health and safety and communities within the vicinity of their mining operations do not bear the brunt of air quality constraints as result of dust generated from their activities.
How can GRT assist silver and zinc mining operations?
Global Road Technology offers GRT Haul-Loc for iron ore mine haul roads, GRT Wet-Loc for workshop, underground roads and the go-line, GRT Ore-Loc for live and dead iron ore stockpiles, GRT Activate for hydrophobic ore materials during crushing and conveying, and even GRT EnviroBinder for post iron ore mining rehabilitation of metalliferous mines.
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REFERENCES
- Jacques et al. 2005. Exploration and discovery of Australia’s copper, nickel, lead and zinc resources 1976-2005. Resources Policy. 30. 168-185.
- Lansdown, A.B.G. 2010. Silver in Healthcare: Its Antimicrobial Efficacy and Safety in Use. Royal Society of Chemistry.
- Mudd, G.M. 2007. An analysis of historic production trends in Australian base metal mining. Ore Geology Reviews. 32. 227-261.
- Sinclair, R.J. 2005. The Extractive Metallurgy of Zinc. The Australasian Institute of Mining and Metallurgy Spectrum Series. 13.
