We self-insure our underground mining equipment. Such equipment is allocated among seven mining units dispersed over ten miles. The historical cost of such equipment was approximately $293 million and $280 million as of June 30, 2023, and December 31, 2022, respectively.

Restricted cash of $4.0 million and $3.4 million as of June 30, 2023, and December 31, 2022, respectively, represents cash held and controlled by a third party and is restricted for future workers’ compensation claim payments and cash collateral to provide power in the MISO grid.