I keep finding these in the basket that is just before the pump (not the skimmer basket). I have found about three of them. They appear to be made of graphite and have a white residue on both sides that I'm not sure what is made of (epoxy maybe?). They break very easily, are very light, but they do not float. They are slightly rounded. I haven't found them anywhere else. I can't for the life of me think what this came from. Anyone know what this is or if I should be concerned? Thanks in advance!