Graphite is used in refractories as a source of carbon. The mineral can be produced from either natural or synthetic sources. Naturally occurring graphite is mined in the form of amorphous, flake or vein graphite, with the former two being the most common. Synthetic graphite is predominantly produced in the form of electrodes from calcined petroleum needle coke, which is crushed, shaped and carbonized over a six-month period into a high-purity, high-cost product. Only natural graphite is used in refractories production; it is lower cost than synthetic graphite and is able to meet the requirements of refractories producers.