Cesium is widely distributed in Earth's crust al very low concentrations. Granites, sea water, and sedimentary rocks contain less than 5 ppm cesium. Mineral springs contain as much as 9mg/l of cesium. Higher concentrations of cesium are found in certain potassium minerals such as the micas, beryl, feldspar, petalite. Some other minerals such as biotite, amazonite, lepidolite or carnalite contain residual concentrations
Only two cesium minerals are known. These are pollucite, a cesium aluminum silicate, and rhodizite, a borate of aluminum, beryllium, sodium and cesium.
The most important deposits of these minerals are located in the United States (South Dakota and Maine), Canada (Manitoba), Southwest Africa (Karib) and Zimbabwe (Bikita).