Magical Opal transformation of Ammonite !!!!!!

Australia is the only place on earth that produces opalized bones of land-living animals including dinosaurs – and most of these are from Lightning Ridge. 

Fossils are preserved here in silica in the form of opal. Some of them are see-through, including the only transparent fossils of large animal bones in the world.

Ammonite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell. 

It is extremely rare for conditions to be right for formation of fossils; and even more rare for opalized fossils to form. Usually, only the hard parts of living things fossilize – for example seed pods, wood, teeth, bones and shells. This often happens after the plant or animal (or a part of it) is buried in sand or other sediments that slowly turn to stone.

Opal forms in cavities within rocks. If a cavity has formed because a bone, shell or pinecone was buried in the sand or clay that later became the rock, and conditions are right for opal formation, then the opal forms a fossil replica of the original object that was buried.

We get opalized fossils of two kinds:

1. Internal details not preserved: Opal starts as a solution of silica in water. If the silica solution fills an empty space left by a shell, bone etc. that has rotted away – like jelly poured into a mold – it may harden to form an opalized cast of the original object. Most opalized shell fossils are ‘jelly mold’ fossils – the outside shape is beautifully preserved, but the opal inside doesn’t record any of the creature’s internal structure.

2. Internal details preserved: If the buried organic material hasn’t rotted away and a silica solution soaks into it, when the silica hardens it may form an opal replica of the internal structure of the object. This happens sometimes with wood or bone. 

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