Silverfish are small, hostile mobs that look more like a strange caterpillar than a fish. They drop nothing when they’re killed, which just makes them more annoying to deal with.
Silverfish only occur in strongholds, making them the rarest mobs in game, after the Ender dragon and spider jockey. The silverfish occupy stone blocks, which look exactly like their normal counterpart. There are 3 types of stone silverfish blocks. Cobblestone, stone and stone brick blocks.
In addition to being inside some stone blocks, silverfish can spawn from the monster spawners inside the strongholds. However, unlike other monsters that spawn from spawners, silverfish cannot spawn within 5 blocks of a player.
When one of those silverfish blocks is mined, the silverfish will pop out and attack the player, causing half a heart of damage. This may seem weak and harmless, but a silverfish takes 2 strikes with a diamond sword to be killed and if a silverfish isn’t killed fast, it’ll ‘call’ other silverfish hiding in other blocks within a distance of 21x11x21 blocks around the silverfish. Before you know it, a huge swarm of silverfish could charge you and overwhelm even well geared players.
If a player manages to get away a short distance from the silverfish, any silverfish that are left alive will occupy any of the three types of stone, if they’re available to them, waiting to be dug up or ‘called’ upon by other silverfish again.
It’s quite easy to find out if a stone contains a silverfish. They may look the same, but the time it takes to mine those rocks is longer when you use a pickaxe and shorter when you use anything else. Simply test out the rock with a pickaxe and leave it alone if you notice it takes longer to mine it.
Getting rid of silverfish inside rocks isn’t too difficult either, all it requires is some brute force, namely a creeper or TNT. The explosion will take out the silverfish with the stone.