Ichthyosaur Fossil
Image: <a href="//commons.wikimedia.org/wiki/User:Bahudhara" title="User:Bahudhara">Bahudhara</a> (CC BY-SA 3.0)
Mineral NameIchthyosaur Fossil
Chemical FormulaSiO2·nH2O
Mohs Hardness5.5
Crystal Systemamorphous
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.1
Colorscream, light brown, iridescent
Transparencytranslucent
Type LocalitySouth Australia
Mineral GroupSilicates (mineraloid)
Usescollector, jewelry
Rarityrare
Description
This specimen displays an opalized Ichthyosaur backbone, consisting of numerous vertebral segments arranged in a long, curved line. The individual vertebrae exhibit a light, creamy-brown color with subtle iridescence, characteristic of precious opal.
Geological Context
Opalized fossils form when silica-rich waters percolate through porous bone material, dissolving the original organic and mineral components and replacing them with amorphous hydrated silica (opal). This process typically occurs in sedimentary environments, often in ancient marine basins, over millions of years.
