Seems Clear to Me, page-13

A report: 'Unfortunately in 2010, the Tanco Mine suffered a "fall of ground" which was followed in 2013 by a second and larger fall of ground. This is due to the fact that the crown pillar of the mine is undergoing compression, causing unstable ground conditions and allowing lake water to enter the mine. These occurrences have curtailed pollucite production and sterilized parts of the ore bodies. Pollucite is the principal ore mineral of Cesium. The Manitoba Department of Mines investigated the cause of the ground falls and determined that the mine was unsafe. It requested that Cabot Corporation develop a mitigation plan. The mitigation plan that Cabot submitted was not satisfactory as it required pumping a large volume of organic rich water into the Bernic River, which is connected to the Winnipeg fresh water supply. Subsequently, the Department of Mines ordered the mine closed. It is now on care and maintenance, and its future ability to provide Cesium to the global market is unknown. Current production from Bernic Lake is from above ground storage and waste piles....'

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I recall a large British oil company almost going bankrupt because they couldn't get enough Caesium Formate and wanted to buy Cabot's total supply - Cabot couldn't do it because they wouldn't have any for other drillers. Doesn't sound too good to me.