Optical crystal Cesium Iodide (CsI) is useful for infrared having transmission through the visible out to 70 µm in a 2 mm thickness. It is principally used for infrared prisms and cell windows. Optical crystal Cesium Iodide (CsI) is also furnished as Thallium activated Cesium Iodide for scintillation crystals. This material has found application in satellite-borne radiation detectors, which must withstand extreme shock and vibration along with rapid temperature changes. Cesium Iodide precipitated powders are used in solid phase pelleting of samples for infrared spectroscopy. Optical crystal Cesium Iodide (CsI) is used in the far infrared as a beamsplitter or as interferometer plates.