Burn hydrogen to make water. Is that artificial water? Or is it forever artificial water? Is all water that mixes with it artificial water? Is all water now artificial since it has mixed with human made water?
While the basic definition seems to be merely "man-made", I would say it holds there is some underlying distinction between the natural and artificial. Natural light vs artificial light -- the two are distinctly different. But are the photons produced by a light bulb artificial, or are they natural photons?
Artificial diamonds are more diamond than diamonds. The diamond portions are identical, regardless of origin.
Or maybe there are trapped gasses or other identifiers left in them that make them distinct. I don't really know about this point.
Anyhow, the natural vs artificial distinction really seems to break down when things are (literally) physically and chemically identical.