Caesium chloride or
cesium chloride, is the
inorganic compound with the formula
CsCl. This colorless solid is an important source of
caesium ions in a variety of applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chlorine ions. Caesium chloride crystals are thermally stable, but easily dissolve in water and concentrated
hydrochloric acid, and therefore gradually disintegrate in the ambient conditions due to moisture. Caesium chloride occurs naturally in mineral waters and as an impurity in
carnallite (up to 0.002%),
sylvite and
kainite. Less than 20
tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral
pollucite.