I've started a new thread for your new identification, as you'd added it to an old thread. This is a septarian concretion. Where did you find it? I will add a factsheet explaining what septarian concretions are when I get to work.
The factsheet explains what these are. This is one of those cases where the cracks in the concretion have been filled in by a mineral that is harder than the rest of the concretion so that when it weathers the cracks weather less than the rest of the sediment and end up standing proud of the surface