Opalized Fossils – How Are They Formed?
A cavity can be formed by a plant or animal being buried in sand or mud and this sand or mud, over time, may become rock. If the conditions are right, opal may form a replica of the original object. For further reading you may find this article on Wikipedia and this article at Australian Geographic of interest.
Australia is the only place on Earth where opalized animal fossils are found. Opalized fossils can be in the form of plants, molluscs, freshwater crayfish, shark teeth, lungfish, bony fish, frogs, turtles, crocodiles, plesiosaurs, dinosaurs, pterosaurs, snakes, birds and mammals. For more details I recommend you read the article at the Australian Opal Centre. I have been fortunate to obtain some magnificent examples of some Opalized Fossils. Three of these are listed below. For more details, please visit my new website at RockyGem.
This opalized shell was mined at Coober Pedy and comes from the famous “Shell Patch Field”. It was unearthed many years ago when the field was at its peak. Today there is little mining there and the good ground is all mined out. Today shells with colour as good as this one are a rarity and with each passing year, they will only become harder to get. Most have been kept in collections and few become available to the market.