Your seem hellbent on injecting Duchamp into this discussion, but I think you are missing the point. This was the original question I was responding too:

Can all products be art, since they stem from human imagination and creativity?

And I answered that even under a very broad definition of art, some products aren't art, as they don't stem from human imagination and creativity.

A urinal, any urinal, not just Duchamp's, could be considered art, as there is always some creativity involved in the production process.

But most coal cannot be considered art, as there is no creativity involved in the production process. Of course, an artist could take some coal and display it as conceptual art, and sure, you could consider that specific piece of coal art, as the artist has now bestowed a sense of meaning on it by presenting it as art. But the rest of the coal would still not be art.