Cesium is rare globally. The United States Department of the Interior included Lithium, Cesium and Tantalum on its list of Critical Minerals (USGS website: https://www.usgs.gov/news/interior-releases-2018-s-final-list-35-minerals-deemed-critical-us-national-security-and, dated May 18, 2018). These “commodities qualify as “critical minerals” because each has been identified as a non-fuel mineral or mineral material that is essential to the economic and national security of the United States, that has a supply chain vulnerable to disruption, and that serves an essential function in the manufacturing of a product, the absence of which would have significant consequences for the economy or national security” (USGS website: https://www.usgs.gov/news/interior-releases-2018-s-final-list-35-minerals-deemed-critical-us-national-security-and, dated May 18, 2018).
There are only 2 pegmatite mines globally that produce cesium:
There is a limited number of companies in the cesium supply chain. Pioneer Resources Limited entered into an offtake agreement with Cabot Specialty Fluids Ltd to sell 100% of the cesium ore extracted from the Sinclair Zone Cesium Deposit to Cabot (Pioneer press release dated June 20, 2018). The Cabot Corporation’s Specialty Fluids business including the Tanco mine was sold to Sinomine Resource Group Co., Ltd. (https://www.businesswire.com/news/home/20190628005482/en/Cabot-Corporation-Completes-Sale-Specialty-Fluids-Business, dated June 28, 2019). Following the sale of Cabot’s Specialty Fluids business to Sinomine, Pioneer Resources has been shipping its pollucite stocks to Sinomine Specialty Fluids Limited (Pioneer press releases dated Aug. 15, 2019 and Sept. 11, 2019).