The South Australian Museum's collection of opals is one of the fastest growing in the world, and houses the two most valuable known specimens of opal in the world - the Virgin Rainbow and the Fire of Australia.

Other strengths of this collection are undoubtedly the fine suites of specimens from South Australian localities. South Australia is famous for its copper mines, particularly Burra, Moonta and Wallaroo, and these are well represented in the collection. There are also collections from the Olympic Dam Copper-gold-uranium deposit, the Precambrian iron formations of the Middleback Ranges and a particularly fine assortment of quartz specimens from the White Rock Quarry in the Mount Lofty Ranges. Targeted field collecting and donations from amateur collectors have meant that the general coverage of species and localities from the state is constantly improving.