How to Add a Custom Ore in Minecraft 26.3 (Fabric)

By Barrett · Published November 14, 2026

Last episode we made the Spore Cluster. Now it needs a source: Mycelium Ore, a glowing fungal ore that only spawns where deep caves expose it, and slowly sprouts little Glowcap mushrooms on top.

What you need: the Sporesteel project from episode 1, Minecraft 26.3, Fabric Loader 0.20.1, Fabric API 0.165.2+26.3 and Java 25.

Register the blocks

Blocks also need a registry key in their properties, and each one gets a BlockItem so you can hold it. Create block/ModBlocks.java:

package com.mineforge.sporesteel.block;

import com.mineforge.sporesteel.Sporesteel;
import java.util.function.Function;
import net.fabricmc.fabric.api.creativetab.v1.CreativeModeTabEvents;
import net.minecraft.core.Registry;
import net.minecraft.core.registries.BuiltInRegistries;
import net.minecraft.core.registries.Registries;
import net.minecraft.resources.ResourceKey;
import net.minecraft.world.item.BlockItem;
import net.minecraft.world.item.CreativeModeTabs;
import net.minecraft.world.item.Item;
import net.minecraft.world.item.Items;
import net.minecraft.world.level.block.Block;
import net.minecraft.world.level.block.SoundType;
import net.minecraft.world.level.block.state.BlockBehaviour;
import net.minecraft.world.level.material.MapColor;

public final class ModBlocks {
	public static final Block MYCELIUM_ORE = register("mycelium_ore", MyceliumOreBlock::new,
			BlockBehaviour.Properties.of()
					.mapColor(MapColor.DEEPSLATE)
					.strength(4.5f, 3f)
					.requiresCorrectToolForDrops()
					.sound(SoundType.DEEPSLATE)
					.lightLevel(state -> 6)
					.randomTicks());

	public static final Block GLOWCAP = register("glowcap", GlowcapBlock::new,
			BlockBehaviour.Properties.of()
					.mapColor(MapColor.COLOR_CYAN)
					.noCollision()
					.instabreak()
					.sound(SoundType.FUNGUS)
					.lightLevel(state -> 10)
					.offsetType(BlockBehaviour.OffsetType.XZ));

	private static Block register(String name, Function<BlockBehaviour.Properties, Block> factory,
			BlockBehaviour.Properties properties) {
		var blockKey = ResourceKey.create(Registries.BLOCK, Sporesteel.id(name));
		Block block = factory.apply(properties.setId(blockKey));
		Registry.register(BuiltInRegistries.BLOCK, blockKey, block);

		var itemKey = ResourceKey.create(Registries.ITEM, Sporesteel.id(name));
		var props = new Item.Properties().setId(itemKey).useBlockDescriptionPrefix();
		Registry.register(BuiltInRegistries.ITEM, itemKey, new BlockItem(block, props));
		return block;
	}

	public static void init() {
		CreativeModeTabEvents.modifyOutputEvent(CreativeModeTabs.NATURAL_BLOCKS).register(output -> {
			output.insertAfter(Items.DEEPSLATE_DIAMOND_ORE, MYCELIUM_ORE);
			output.insertAfter(Items.RED_MUSHROOM, GLOWCAP);
		});
	}

	private ModBlocks() {}
}

lightLevel makes both blocks glow, and useBlockDescriptionPrefix lets the item reuse the block’s name.

The ore that grows mushrooms

MyceliumOreBlock extends DropExperienceBlock so it drops 1–3 XP, and uses random ticks to sprout a Glowcap on the open block above it:

package com.mineforge.sporesteel.block;

import net.minecraft.core.BlockPos;
import net.minecraft.server.level.ServerLevel;
import net.minecraft.util.RandomSource;
import net.minecraft.util.valueproviders.UniformInt;
import net.minecraft.world.level.block.DropExperienceBlock;
import net.minecraft.world.level.block.state.BlockState;

public class MyceliumOreBlock extends DropExperienceBlock {
	public MyceliumOreBlock(Properties properties) {
		super(UniformInt.of(1, 3), properties);
	}

	@Override
	protected void randomTick(BlockState state, ServerLevel level, BlockPos pos, RandomSource random) {
		BlockPos above = pos.above();
		if (random.nextInt(4) == 0 && level.isEmptyBlock(above)) {
			level.setBlockAndUpdate(above, ModBlocks.GLOWCAP.defaultBlockState());
		}
	}
}

The Glowcap

The Glowcap is a small plant that can only stand on Mycelium Ore:

package com.mineforge.sporesteel.block;

import net.minecraft.core.BlockPos;
import net.minecraft.world.level.BlockGetter;
import net.minecraft.world.level.block.Block;
import net.minecraft.world.level.block.VegetationBlock;
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.phys.shapes.CollisionContext;
import net.minecraft.world.phys.shapes.VoxelShape;

public class GlowcapBlock extends VegetationBlock {
	private static final VoxelShape SHAPE = Block.box(5, 0, 5, 11, 8, 11);

	public GlowcapBlock(Properties properties) {
		super(properties);
	}

	@Override
	protected boolean mayPlaceOn(BlockState state, BlockGetter level, BlockPos pos) {
		return state.is(ModBlocks.MYCELIUM_ORE);
	}

	@Override
	protected VoxelShape getShape(BlockState state, BlockGetter level, BlockPos pos,
			CollisionContext context) {
		return SHAPE;
	}
}

Models, textures and names

Each block needs a blockstate, a block model and an item model file. The ore is a full cube in assets/sporesteel/models/block/mycelium_ore.json:

{
  "parent": "minecraft:block/cube_all",
  "textures": {
    "all": "sporesteel:block/mycelium_ore"
  }
}

The Glowcap uses the crossed-planes model that flowers use, in models/block/glowcap.json:

{
  "parent": "minecraft:block/cross",
  "textures": {
    "cross": "sporesteel:block/glowcap"
  }
}

And each blockstate points at its model, for example blockstates/glowcap.json:

{
  "variants": {
    "": {
      "model": "sporesteel:block/glowcap"
    }
  }
}

Add both names to en_us.json:

{
  "item.sporesteel.spore_cluster": "Spore Cluster",
  "block.sporesteel.mycelium_ore": "Mycelium Ore",
  "block.sporesteel.glowcap": "Glowcap"
}

Mining tags and loot

Because the ore uses requiresCorrectToolForDrops, the game needs to know which tool is correct. Add it to data/minecraft/tags/block/mineable/pickaxe.json and data/minecraft/tags/block/needs_stone_tool.json:

{
  "replace": false,
  "values": [
    "sporesteel:mycelium_ore"
  ]
}

The loot table in data/sporesteel/loot_table/blocks/mycelium_ore.json drops the ore with Silk Touch, otherwise 1–3 Spore Clusters boosted by Fortune:

{
  "type": "minecraft:block",
  "pools": [
    {
      "rolls": 1,
      "entries": [
        {
          "type": "minecraft:alternatives",
          "children": [
            {
              "type": "minecraft:item",
              "condition": "minecraft:tool/can_silk_touch",
              "name": "sporesteel:mycelium_ore"
            },
            {
              "type": "minecraft:item",
              "name": "sporesteel:spore_cluster",
              "modifier": [
                { "type": "minecraft:set_count", "count": { "type": "minecraft:uniform", "min": 1, "max": 3 } },
                { "type": "minecraft:apply_bonus", "enchantment": "minecraft:fortune", "formula": "minecraft:ore_drops" },
                { "type": "minecraft:explosion_decay" }
              ]
            }
          ]
        }
      ]
    }
  ]
}

World generation

The configured feature says what to place: veins of up to 6 ore replacing deepslate, in data/sporesteel/worldgen/feature/mycelium_ore.json:

{
  "type": "minecraft:ore",
  "size": 6,
  "discard_chance_on_air_exposure": 0.0,
  "targets": [
    {
      "state": "sporesteel:mycelium_ore",
      "target": {
        "predicate_type": "minecraft:tag_match",
        "tag": "minecraft:deepslate_ore_replaceables"
      }
    }
  ]
}

The placed feature says where: 40 tries per chunk between 8 blocks above bedrock and Y −8, and only where at least one side touches air, so every vein is exposed in a cave. In worldgen/placed_feature/mycelium_ore.json:

{
  "feature": "sporesteel:mycelium_ore",
  "placement": [
    { "type": "minecraft:count", "count": 40 },
    { "type": "minecraft:in_square" },
    {
      "type": "minecraft:height_range",
      "height": {
        "type": "minecraft:uniform",
        "min_inclusive": { "above_bottom": 8 },
        "max_inclusive": { "absolute": -8 }
      }
    },
    {
      "type": "minecraft:block_predicate_filter",
      "predicate": {
        "type": "minecraft:any_of",
        "predicates": [
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [0, 1, 0] },
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [0, -1, 0] },
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [1, 0, 0] },
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [-1, 0, 0] },
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [0, 0, 1] },
          { "type": "minecraft:matching_block_tag", "tag": "minecraft:air", "offset": [0, 0, -1] }
        ]
      }
    },
    { "type": "minecraft:biome" }
  ]
}

Finally, add the placed feature to every Overworld biome in world/ModWorldGen.java:

package com.mineforge.sporesteel.world;

import com.mineforge.sporesteel.Sporesteel;
import net.fabricmc.fabric.api.biome.v1.BiomeModifications;
import net.fabricmc.fabric.api.biome.v1.BiomeSelectors;
import net.minecraft.core.registries.Registries;
import net.minecraft.resources.ResourceKey;
import net.minecraft.world.level.levelgen.GenerationStep;
import net.minecraft.world.level.levelgen.placement.PlacedFeature;

public final class ModWorldGen {
	public static final ResourceKey<PlacedFeature> MYCELIUM_ORE =
			ResourceKey.create(Registries.PLACED_FEATURE, Sporesteel.id("mycelium_ore"));

	public static void init() {
		BiomeModifications.addFeature(BiomeSelectors.foundInOverworld(),
				GenerationStep.Decoration.UNDERGROUND_ORES, MYCELIUM_ORE);
	}

	private ModWorldGen() {}
}

Call ModBlocks.init() and ModWorldGen.init() from onInitialize, right after ModItems.init(). Create a new world (existing chunks don’t regenerate), dig down past Y 0 and look for the glow.

Recap

You added a glowing ore that only spawns on deep cave surfaces, grows Glowcaps, needs a stone pickaxe and drops Spore Clusters. Next episode we turn those spores into metal with the Culture Vat.