Duplicate ores in your modpack: why you have five kinds of copper

You mine copper. It isn't the copper your machine wants. Your chest now has three kinds of copper ore, four copper ingots and two copper dusts, and your recipe viewer shows ten ways to make a copper plate. If you've played a home-made pack with a few tech mods, you've met this.

Why it happens

Mods are made by different people, and each one needs to work on its own. A tech mod that uses tin can't assume another mod adds tin, so it adds its own: its own ore in the world, its own ingot, its own dust, its own block. Put three such mods together and you get three tins.

Minecraft does have a system for this. Mods can label their items with shared tags (for example "this counts as a tin ingot") so another mod's recipe accepts any tin. Most good mods use them. But they don't catch everything:

• Some recipes ask for one specific mod's ingot, not "any tin ingot".
• Each mod's ore still generates in the world, so you get several copies.
• Machines that process ore output their own mod's version.
• Loot chests and villager trades hand out whichever version the mod chose.

Why it matters

It's more than clutter:

• Chests fill up with near-identical items that don't stack.
• Automation breaks when a machine outputs the "wrong" copper and the next machine won't take it.
• The world feels off, with ore everywhere because several mods are each generating their own.
• Progression can wobble. If one mod's version of a metal is cheaper to process, it can turn into a shortcut.

How pack makers fix it: unification

The fix is called unification: pick one version of each material and make the pack use it everywhere. Done properly, that means:

1. Choosing one "kept" item for each material, usually from the most-used mod.
2. Changing recipes so they make the kept item, and accept any version as an ingredient.
3. Stopping the extra ores from generating, so the world only has one of each.
4. Changing loot tables so chests give the kept item.
5. Adding a way to convert leftovers, for things that can't be changed, like villager trades.
6. Hiding the retired items from the recipe viewer, so they stop cluttering searches.

There are mods that do parts of this automatically, and pack makers often write scripts for the rest. The difficult part is being thorough: missing one recipe, one loot table or one machine output brings the duplicates back. There's also a trap the other way. Some items are tagged as a material but are actually an upgrade (a magic-infused version of a gem, say), and unifying those by mistake breaks the mod that made them.

How Packspire handles it

Packspire reads every recipe, loot table and tag the game actually loads in your pack (not just what the mods say they add), finds the duplicate materials, and unifies them: recipes, ore generation, loot and conversion recipes for what can't be changed. It leaves upgrades that only look like duplicates alone. Retired items are hidden from JEI and EMI, achievements and quests that asked for a retired item accept the kept one, and every fix is checked in the running game before the pack ships.

You end up with one copper. Build a pack and see, or read about the other things that go wrong when you make a modpack yourself.

Frequently asked questions

What is unification in a Minecraft modpack?

Making the whole pack use one version of each shared material, such as one copper ingot, across recipes, ore generation, machine outputs and loot, so duplicates stop appearing.

Is there a mod that unifies ores automatically?

Yes. Almost Unified is a popular one for NeoForge and Fabric: it changes recipes and hides duplicates from recipe viewers. Pack makers add scripts or other mods for what it doesn't cover, such as ore generation and loot.

Why can't I craft with another mod's copper ingot?

The recipe asks for that mod's specific item instead of the shared "copper ingot" tag. Unifying the recipe to accept the tag fixes it.

Does removing duplicate ores break existing worlds?

Ore already generated stays in the world, and items from a removed mod disappear. Back up a world before unifying a pack mid-game, and keep a conversion recipe for leftover items.

Sources

• Almost Unified
• Polymorph, for choosing between recipes that share a layout