Around 3cm big dark green, is this stone???

I have done my 4th flush today and passed several small green stuf, along with it I found one big around 3cm with light green around. I took is separately to know is this a stone or what?

I could not just desolve it with water, I use screwdriver to brake that and was bit hard to break and found very very dark geen inside. Is that do you think a Stone??? I don't know where it comes from, I only know have a small Polyp in my Gallbladder and was trying to get rid of the same. Would be very happy if the stone I saw was a polyp.


Thanks