This is a part of an opalized tree, and the rings you see are actually tree rings; or at least they were.
This is an very rare sample: opal can be fairly common in petrified wood, but this is a fire opal, which makes it so much more valuable. Fire opals are transparent to translucent opals with warm body colors of yellow, orange, orange-yellow or red – basically, it often has pretty colors.
So how did this magnificent opalized tree came to be? Initially, water filled the cracks and empty spaces of the source fossil, and the silica content in the water hardened and turned into opal or chalcedony.
Andrei's background is in geophysics, and he published his first scientific paper when he was still an undergrad; now, his main focus is on how geology and geophysics can be applied to understand and protect the environment. Feeling that there is a gap between scientists and the general audience, he started ZME Science - and the results are what you see today. 
Tip us on news, scientific reports and studies, scientific advances, science art, interesting phenomena or any kind of science related material. Just write to
Published on Tue, Nov 12, 2013 by Mihai Andrei
Post filled in: GeoPicture