Minecraft wiki entry for Magma_Cube, associated text: Magma cubes.
Size comparison between a large magma cube and a player.
They emit the same flame particles as a mob spawner upon landing.
A group of small magma cubes.
A separated magma cube. Note the lava core.
A magma cube leaping out of lava.
A magma cube spawner inside a Bastion Remnant.
A magma cube spawner completely disabled with 9 solid blocks in Java Edition.
A magma cube spawner in a bastion remnant, being disabled with solid blocks.