Iridium is primarily used in high-performance applications due to its exceptional resistance to heat, corrosion, and wear. It is a key component in crucibles used for growing single crystals, especially in the semiconductor and lighting industries. Iridium is also used in spark plugs for aerospace and high-performance engines because it maintains structural integrity at very high temperatures. It serves as a catalyst in certain chemical reactions, particularly in the production of acetic acid. Due to its stability and durability, iridium is used in medical devices such as electrodes for pacemakers and in radiotherapy equipment. Additionally, it is employed in deep-sea and extreme-environment instrumentation, including electrodes for deep-ocean monitoring systems. Iridium alloys are used in pen nibs, compass bearings, and other precision instruments where wear resistance is critical.