nofearluc

Hello, My parents have this strange rock lying around and I am wondering if anyone could identify it (see pictures). It's a small, grey rock with orange tints and it has a distinguishable comic shape. The cone edges are smooth. The bottom seems to be broken off from somewhere and has a very particular pattern. From the core there seems to be lines protruding circular around the centre point. Sort of 'fanning out'. The space between the grey rock seem to be filled up with some type of beige curd sand. The top seems to be somewhat bruised and shows a spiral pattern going downward to the bottom. The core seems to be glacy like flint stone. It was probably found somewhere along the coast of Zeeland in The Netherlands. These may be manually deposited sediments. Could anyone help me out and identify this rock object? My guess is that it's part of a stalagmite but it doesn't seem to be just chalk... Cheers, Luc