Which materials can I use as a layer?

Any that have a height type slot on your map — not just the base game ones.

How to see what works

The editor shows you your map's material pool. Anything listed without (!) can be set as a layer and dumped again. Anything marked (!) has no slot left on that map — see the explanation of the 63 limit.

Map-specific materials

If your map ships its own materials, you can use them. For now you have to enter them by hand in miningLayers.xml.

Planned: that the editor offers your map's materials directly instead of you typing them out. It is on the list but not built yet — which is why it says plan here, not promise.