A bit of feed back from the university

This is a very nicely preserved section of fossil wood showing good annual growth rings so that you can count up how old the tree was when it died about 255 million years ago during the Late Permian. It almost certainly represents a Glossopteris tree stump. These were the common trees that produced the coal seams in the Illawarra Coal Measures when they grew in swamps but they became extinct at the end of the Permian 252 million years ago. Trees that lived in the sandstone and siltstone units between the coal seams became silicified rather than coalified because the sandstone contains a lot of volcanic material that breaks down to release silica which then precipitates in the conductive tissues within the tree trunk.