In Norfollk (England) there are beaches where the tide has washed away the chalk and left some extraordinary flint formations – see www.geulogy.com/norfolk/beestonbump/flintbackbones-beestonebump.html …
Flint backbones are usually found alone – but can also be found attached to flint circles. These circles have chalk inside them, similar to the hollow centres of pot stones. How are these formations made and is electro magnetism involved? See for instance, https://en.wikipedia.org/wiki/Flint (and the second paragraph on strange flint formations in Norfolk. See also www.northfolk.org.uk/geology/sheringam-beeston.html