Silver’s (Ag) relative scarcity, attractive appearance and malleability for easy shaping has made it suitable for use in jewellery, ornaments and silverware since before ancient Roman times. Its use has been extensive in coins throughout history, although this application has declined in recent times. In Australia, the 1966 50cent piece was the last coin in general use to contain silver (80% silver, 20% copper). Although silver is resistant to oxidation it readily forms a surface tarnish of silver sulphide. While its high electrical and thermal conductivity make it useful in the electronics industry, the largest use of silver is in photographic paper and film.
Silver is commonly extracted from ore by smelting or chemical leaching. Ore treatment by mercury amalgamation, such as in the patio process or pan amalgamation was widely used through the 1800s, but is seldom used today.
Silver is also produced during the electrolytic refining of copper and by application of the Parkes process on lead metal obtained from lead ores that contain small amounts of silver. Commercial grade fine silver is at least 99.9 percent pure silver and purities greater than 99.999 percent are available.
The upper parts of the Broken Hill deposit and the Mt Isa deposit discovered in 1923 by John Campbell Miles were very rich in silver, the prime commodity sought in the early days. The wealth generated by mining the Broken Hill ore allowed The Broken Hill Proprietary Company Limited to prosper and, although it no longer has an interest in the deposit, its successor, BHP Billiton has become one of Australia’s largest companies.
The rich lead-silver lodes discovered by John Campbell Miles at Mt Isa remain in production after more than 80 years of mining. Discovery of the nearby rich Hilton deposit occurred in the late 1940s but it was not developed until the mid 1980s. In the Mt Isa region, there are large mines at the George Fisher (adjacent to Hilton), Cannington (very rich), and Century deposits, while the Dugald River and Lady Loretta deposits are yet to be mined. In the Northern Territory, the huge McArthur River lead-zinc-silver deposit is a major producer.