Caption:
Olympic Australis opal, the largest and most valuable gem opal ever found. It was discovered in the Eight Mile opal field in Coober Pedy, Australia, in 1956. It weighs 3540 grams (17,000 carats) and is 28 centimetres long. It is kept in the showroom of Altman and Cherny Pty Ltd., an opal company in Melbourne, Australia.