The Australian Opal. On the 1st of February 1915, 14-year-old Willie Hutchinson was searching for water in the Australian Outback. Suddenly the boy came across small white glimmering stones, unlike anything he’d seen before. Willie had just discovered what would become Coober Pedy, the world’s largest opal field (which today cover 5000 square km). Coober Pedy takes its name from the aboriginal words Kupa (white man) and piti (hole). Australian Opals are usually a clear or whitish colour but can also produce rainbow colours. Australia produces approximately 80% of the world’s opals, with most of them coming from Coober Pedy, 800km north of Adelaide. When Queen Elizabeth of the UK visited Australia in 1954 the South Australian Government presented her with an opal necklace.
The Australian Opals formed approximately 100 million years ago, then the Eromanga Sea covered the entirety of central Australia. However, this sea began to dry out, leading to acidic fluids dissolving silica from sandstone. This silica-rich solution was then precipitated as opals (also known as hydrated silica as opals are a hydrated amorphous form of silica).
Australia is so proud of the opal it is named as their national gemstone. New proposals, however, have been put forward to name it as a Global Heritage Stone Resource (GHSR). The GHSR award is designed to name stones which are significant to human culture, particularly those commonly used in building such as the Portland Stone and Sydney Sandstone. About a dozen famous stones, such as famous building stones like the Carrara Marble and Portland Stone, have currently been named.
Some geologists, however, disagree about the proposal for opals inclusion. Their use in jewellery and the fact they are too varied in their form and colour to give a strict description, leads to many geologists to believe they fall outside the categories of the original idea of the GHSR.
