The original aragonite internal shell dissolved and was replaced by opal in these belemnite fossils. They existed the Cretaceous Period. Fossils were found in Coober Pedy, Australia. Specimen was on display at the Muséum National D'Histoire Naturelle Minéralogie et Géologie in Paris France (August 2016).
http://www.mnhn.fr/fr/visitez/lieux/galerie-mineralogie-geologie
