There aren't any wineries in the Slate Valley of Vermont but a friend of mine passed along a bottle of Clean Slate, a Riesling from Mosel, Germany. I found the artwork simple and clever - the Mosel River meandering through blue-green slate. However, I followed the path of the Mosel and the artwork doesn't match up with any actual meanders, kind of a disappointment. I did a little digging to see if I could determine the origin of the "steep slate hills" and I think the slate in question is part of the Hunsrück Slate formation; I found references to a Mosel and Moselle Slate but I think they were common names not formations. Apparently the Hunsrück preserves a pretty spectacular fossil record and is an important Konservat-Lagerstätten.
I wasn't able to find a great geologic map or any articles describing other slate formations - clearly my weak German is at fault here - help out if you know of other resources! I did find the following map, which should help contextualize the location and geology a little bit:
So it appears lithology is where the similarities end between the Slate Valley of Vermont and Mosel Valley of Germany - they are different ages (Cambrian versus Devonian), one preserves fossils another preserves nothing, and the steep valley walls of the Mosel offer stark contrast to the rolling hills of Vermont. However, the wine was pretty decent!