Magma Stone is a particular type of glowing, magma-like rock that can only be crafted from one block of stone, and one Lava sacs. The lava sac may also be substituted with ten buckets of lava. Sometimes magma stone forms when a magma flows into a water source block, but this is rare. You also can only mine magma stone with a gold pickaxe, and nothing else.
When a mob or monster touches this block, it will start to burn, or even die immediately, but it will not burn items, making it great for mob grinders, defensive walls, or even protecting your stuff from other players in multiplayer.
This can be used as a super-strong building material or as a unique decoration. It is also excellent as traps or mob grinders.