Is there any API I could use to add materials? And if so, where is it located?

There's no formal API available yet, but you can look into the lib.materials package of the source code to see how the materials are handled and added. If you've ever worked with Tinkers' Construct, it's largely the same just with different types of material stats added.

Quick question, is there any place I can contact you, outside of the issues, mostly so I can discuss stats for the materials xD

As it pains me to say this.. is there a maven repo for the mod that I could use? Can't really figure out how to add this to my libraries 😢 though at least I figured out how to add the stats (not really that hard). Was looking to add compatibility for most metals xD so just need to register everything with your stats and parts.

Sorry, no maven repo or anything like that yet. You'll either have to figure out how to add this as a library as it is, or wait until the mod's a little more fleshed out with a proper API structure.

Managed to add your mod as library :)

If you have a CurseForge account, you could PM on there. Otherwise, you could e-mail me at [email protected].