Deposit Type The geology of the potash-bearing beds of the Carlsbad area has been well documented. Overall, the potash-bearing beds may be described as bedded sedimentary rocks, deposited across the Delaware Basin and Northwest Shelf backreef from the Capitan Reef. The depositional sequences that developed in the Salado Formation consist of repetitive cycles that can be recognized by changes inmineralogy, sedimentary textures, and structures. Two types of cycles are differentiated Type I and Type II. A complete Type I cycle rangesin thickness from 3 ft to 33 ft and consists of (in ascending order): • A basal, mixed siliciclastic and carbonate mudstone • Laminated to massive anhydrite-polyhalite • Halite • Halite with mud (argillaceous halite) Type II is a thinner, less complete sequence and consists of halite that grades upward into argillaceous halite (Lowenstein 1988).The anhydrite-polyhalite beds are laterally continuous over large distances and are used as marker beds for correlation. Potash beds arenot included in these sequences because potash is secondary and formed later than the basic depositional sequence. The HB Mine, which was formerly mined on the 1 and 3 ore zones (Barker and Austin 1999),has been flooded and is currently being solution mined with brines to obtain potash from the remaining pillars. Mineralization In the Carlsbad Area, the potassium minerals, in order of decreasing abundance, are polyhalite, sylvite, carnallite, langbeinite,kainite, and leon ........

The HB Plant produces Muriate of Potash (MOP) from the solution mine brine. The long-term underground mining plan includes development and high-extraction, room-and-pillar mining in the 3, 4, 5, 7, 8, and 10 ore zones. Solution mining of the 1 and 3 ore zones in previously mined-out areas of the property is planned to continue long term. All MOP production at IPNM comes from the HB Solar SolutionMine in the 1 and 3 ore zones. Historical room-and pillar-mining operations at the HB complex recovered about 70% of the ore, leaving approximately 30% of the ore available for secondary recovery in pillars plus what can be recovered beyond the limits of the conventional mine works. Mining at the HB Solar Solution Mine recovers potash by injecting saturated saline NaCl brine into the old mine works to create underground leach lakes. Over time, the solution enriched with potash is pumped to the surface to solar evaporation ponds. Selective solar evaporation leaves behind a potash-enriched salt that is collected using scrapers, pumped and processed at the HB Plant. The solution mine comprises six injection wells, five extraction wells, and three monitoring wells.

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