Philosopher's Stone is an item from the Equivalent Exchange mod and is a more durable version of the Minium Stone. It can change materials into other similar base materials (ex: cobblestone into stone) by placing them in a Crafting Table.
This item also allows to convert certain ingots (ex: gold to iron or iron into gold) and smelt ores at the cost of Coal. Thus placing a Philosoher's Stone, one Coal and 7 iron ores in a Crafting Table will yield 7 iron ingots. Most Minium Stone recipes will work using a Philosopher's Stone.
Note that the recipe below will only work in EE2. The recipe will not work on modpacks that have EE3, like the Ultimate Pack.