I have my custom mod pack installed on Minecraft 1.6.4 server and client. THe proble is - when I mine Moonstone Ore from ARS Magica 2 I get Invalid Item (Destroy) from Thermal Expansion instead of Moonstone:

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What can be the reason and how to fix that?

  • 2
    This is an ID conflict. You'll have to modify one of the config files to change the ID of one of these items to some new unused ID. I don't have time now to make a full answer though.
    – Arperum
    May 14, 2014 at 7:56
  • @Arperum, I have tried what you suggested and it helped. If you find some time and post your comment as an answer I will mark it as accepted one.
    – Dmytro
    May 23, 2014 at 15:23

2 Answers 2


This is a clear case of an ID conflict.

The Ars Magica moonstone item uses the ID 20256, but this same ID is also used by Thermal Expansion for that "Destroy" item (that is probably used for something hidden in Thermal expansion). The Thermal expansion item is used because these are loaded later in the boot order (loading order is alphabetic over the jar/zip files as far as I've seen)and thus overwrite the previous Ars Magica item.

The solution to this is to modify the Ars Magica or the Thermal expansion config file so it uses a different ID for this specific item. Keep in mind that some mods require their itemID's to be sequential, so modifying one requires you to modify the other ID's in the sequence too(I don't know if this goes for Ars Magica and/or Thermal expansion though)


After some thinking I solved the problem: I opened the config file from Ars Magica and changed the value of "I:ItemIDRangeStart" on the section "items" for some other value, (I used 19744) and then deleted the list of IDs on the same section. By testing, I confirmed that I was able to craft the moonstone as it should be, I even placed the block on the world and broke just to make sure. After it I just trowed the "invalid" items on the lava and spawned the right ones to make it even. The last step is to turn the config "B:RetroactiveWorldGen" to true so you can get the blocks affected by the ID change on the already loaded chunks. Don't forget to backup all the process and good luck :)

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