So in this case instead of the bones getting fossilized by the replacement of bone material with a fossilizing mineral this mineral collected AROUND the bones instead and built up a rounded casing for them? So inside these concretions are unfossilized bones? Why the different process?
AbE watched it again. There's one point where they say the bones were ALSO fossilzed so I guess that answers my question. Why they also formed this ball of mineral within the rock is still a question though.
There was interesting research on this question recently too. Bunch of researchers from Japan argue that it's due to the release of calcium from bones interacting with clay of certain chemical compositions; and that these calcite concretions probably only take a few years to form.
Full article in
Nature here (open access).
Summary in
Forbes magazine here
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