I just did some of them and it's a nice item. The ones I found recipes for are protection and resistance. Then I started out to find new ones. Just by trying combinations 1. small block of clay cheapest gem, 2. same with block of clay, 3. same with large block of clay. I went up the cheap gems like this without finding a new recipe. To go all the way up I decidied not to do, because I am sure that somebody has tried already. So up to now we seem to know that wolf's eye agate and carnelian work. Whoever has tried and knows what else does not work please post it here. Of course if you found a new recipe.
I would be ready to join forces in a research project on this issue. Maybe some gems work with skins. Maybe there is only one more. I doubt at least that there are only two.