Oil

Was quite taken with the oily residue that has formed on the water in one of the tubs we are storing the stone chips in.

Not really sure if it is from the stones that we have dug up after years at the side of the old patio or the residue from the manufacture of the big black tub we bought to hold them in. What do you think?

Hope the weather holds so we can finally do the foundation for the new wall.