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Umoona Mine

Hutchison street, Coober Pedy, South Australia state, Australia

Occurrence

Groundwater deposition

Opal, chalcedony, and gypsum formed in cracks during weathering and diagenesis processes in the Early Cretaceous Aptian (120 Ma) Bulldog Shale of the Marree Subgroup. The Bulldog Shale was formed under shallow marine environment and produces a lot of fossils. Fossils were replaced by opal during the diagenesis process. The Marree Subgroup overlies unconformably the Late Jurassic Algebuckina Sandstone and Paleozoic sediments.

Umoona Opal Mine

Outcrop of a vein of precious opal displaying play of color. The pale brown host is weathered shale of the Cretaceous Bulldog Shale.

Reported Minerals

  • Opal

Mineral Assemblages

  • Opal - Gypsum
  • Limonite - Opal

Localities

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