Iron-carbon alloy- that is iron with more than 2% carbon in it. Not only does the carbon make it easier to cast (put in a mold) but it makes it virtually indestructible! It can handle incredibly high temperatures and rough handling without any issues.  The cast iron is poured into a sand mold (a very environmentally friendly process) and heated to make these beauties. The raw pan is not going to behave very well until the cast iron is “seasoned” with oil (this is what gives it that dark glossy finish!). Cast iron can go anywhere - stove or inside your oven. Just don’t put it into your dishwasher!