I wonder if people could help identify this rock. It was found in cothi river in wales, it seems that the main part of rock is some sort of soft sediment, while the pattern ridges are made of crystal or something harder. The pattern continues all around the stone and repeats itself in similar fashion. It is about 5 inches long across.
and much of the misinformation is copied between different sites.
Also, the word 'septum' has nothing to do with 'sept' meaning seven.
If you fancy breaking or sawing your specimen open, please show us a photo of its interior. Sometimes they are rather impressive. They used to use slices of good ones as small table tops because the patterning was so fascinating.