Old Timers Mine
Crowders Gully road, Coober Pedy, South Australia state, Australia
Occurrence
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.
Outcrop offibrous gypsum in cracks of weathered shale. The pale brown host is weathered shale of the Cretaceous Bulldog Shale. This type of gypsum is produced in cracks near the ground surface.
Reported Minerals
- Opal (after bivalvia fossil)
- Gypsum
Mineral Assemblages
- Opal - Gypsum
Localities
- Shimo-jinya (Conglomerate, Lithiophorite)
- Mount Orihime (Chert, Lithiophorite)
- Masaka (Chert, Lithiophorite)
- Umoona Mine (Opal deposit)
- Old Timers Mine (Gypsum, Fibrous)
- Opal Quest Mine(Gypsum, Rosette)
- Moon plain (Gypsum, Tabular)
- Jweller's shop noodling area (Chalcedony)