Sorry guys for the confusing pics. It is one color throughout, green. Its just looks like 2 colors since one side has been flattened and one is the way it came and has some dirt and such from over the years built up on it. It is definitely finer than the swaty, And I would guess it to be natural, based on the fact that there are small variances in the color in it, even beneath the surface after I lapped it. I dont know o any proper way to check if its a natural stone though.