Found this very round flint stone (about 10cms across ) in my garden at St Olaves, Great Yarmouth, Norfolk. Looking at other posts it would appear to be a fossilised sea sponge. Please advise whether this is correct and approximately what age (100million years old?). Many Thanks. I have attached a couple of photos
i think its unlikely to be a sponge, sponges usualy have one very large hole at the top where all the water flows out of the sponge. that is how they feed; filltering the water of its particals and venting the water out through the hole.
it looks to me to be a rounded flint bolder, probably has spent a very long time in a river or on the beach being ground into this shape.
maybe it was its shape that someone liked and brought it back as a garden ornament?