Iridium is mainly used in creating alloys. Since these alloys are very expensive, they are only used for special purposes. Helicopter spark plugs are made of an iridium-platinum alloy, which helps them ignite their fuel and take off. Iridium is also used for special types of electrical wires, electrodes, and electrical contacts, all important for circuit breakers and energy transference. An unstable isotope of Iridium, Iridium-192, is used for X-rays and for treating cancer.