In stainless steel. Definitely a rough feel, craters are quite subtle but are lovely when it is picked up and looked closely. Nice weight and size for me - I wear it long; hanging to just below my sternum.
On one side (thankfully the "blank" area) there is a patch that sort of looks like it has been polished in that spot, but then was stopped before the rest of it was polished. I'm not sure if that's what it is, or if it's something to do with the production process - not a huge problem for me, you have to expect these things when you are the first to try.
Overall, a very nice pendant, I'm very happy with it! I love that it has the real moon's details! I'll post more comments with other photos (I can't seem to attach more than one to this comment)