Archaeology !

So any ideas on this ?

......whilst digging in the garden recently ,I pulled this strange object out of the earth .

It is about 4 0r 5 inches long and an inch or so wide .

You may not be able to see from this picture , but there is a distinct groove going length ways along it on one side . It feels smooth to hold in the palm of the hand . The ends are rough and give it a bone like appearance . My thoughts are that it might be a WHETSTONE , used to sharpen the blade of a cutting tool . I will be taking it to the museum to be looked at along with a rock which maybe a roughout for a stone axe that I found in another part of my garden . Sorry no pic of this yet and it maybe nothing anyway !