Mycelium will grow on any dirt block in an area where other mycelium blocks exist, even if the dirt blocks have a sapling or another plant on it (although the plant will fall off as soon as mycelium appears). Mycelium will spread to adjacent dirt blocks, as long as enough Light reaches the block (light level 9). Its spread can be stopped by creating an obstruction to the mycelium's expansion, such as a two-block change in terrain height or a non-dirt block.
Small "spore-like" particles appear above the surface of mycelium blocks. It is the only block beside giant mushroom blocks and dirt blocks that appear on the surface of the mushroom island.
- Mycelium was first added in the first Beta 1.9 release, but it was only usable in Creative.
- As of 1.2.4, mycelium is the only block on which players can spawn mushrooms while in sunlight.
- They were added to Pocket Edition in the 0.9.0 update, along with mushroom island biomes.
- When harvested, the mycelium will normally drop a dirt block, but if it is mined using a tool with the Silk Touch enchantment, a block of mycelium can be collected instead.
- Mycelium can spread to dirt blocks in alternate dimensions, such as the Nether.
- Mycelium is the rarest variant of dirt in the game.
- Considering it's only found in 1 biome, and that biome is the second rarest one in the game.