In this case, I do not see anything particularly useful, however.So, it may be be a flint that is spherical by chance (they do come in all shapes and sizes).But it could also be a fossil sponge, like the one IDd and very well explained by Luanne on this forum a couple of years ago- <a href="http://www.nhm.ac.uk/natureplus/thread/4319">http://www.nhm.ac.uk/natureplus/thread/4319</a> BTW, such flints can have archaeological significance, too- http://finds.o