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 in mineralogy, sedimentary textures, and structures. Two types of cycles are differentiated Type I and Type II. A complete Type I cycle ranges in 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 are not included in these sequences because potash is secondary and formed later than the basic depositional sequence.

Mineralization
In the Carlsbad Area, the potassium minerals, in order of decreasing abundance, are polyhalite, sylvite, carnallite, langbeinite, kainite, and leonite. Other potassium minerals occur only in minor amounts in association with the principal potassium minerals listed previously.

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The East Mine is a high-extraction, mechanical room-and-pillar mine. Potash was the primary product until mining progressed to the mixed langbeinite and potash ore in the 5 ore zone. The mixed ore was processed into two products: MOP sourced from the sylvinite portion of the mixed ore, and Trio® sourced from the langbeinite portion of the mixed ore. The East Mine plant was converted to a langbeinite-only operation in April 2016 and potash is no longer produced from the East Mine. The maximum productive capacity of the plant is 400,000 t of Trio® concentrate annually.

There are five active sections with a miner and a shuttle car loading onto a belt conveyor. Each mining section produces approximately 240,000 t of run-of-mine ore each year. The long-range production balanced with sales projections results in a long-term annual production of 1.2 Mt of ore for 250,000 t of Trio® annually.

Equipment: Continuous miners and shuttle cars.

The East Plant was modified in 2003–2004 to allow dual processing to recover the K2O value from both the sylvite and langbeinite fractions of the ore. In 2016, the sylvite circuit was permanently closed. Langbeinite, marketed as the organic fertilizer Trio® brand of products, is recovered using dense media separation and a fine langbeinite recovery circuit.

Currently about 1 million tpy (Mtpy) of ore is processed at a rate of 300 tph. The ore is crushed, screened, pulped, and rescreened. Coarse material is forwarded to the dense media separation (DMS) circuit. The DMS concentrate is water leached, debrined, and dried.The coarse product is separated into the three Trio® products. Fine material from the screening process is recovered using gravity separation, leaching, debrining, and drying. Fine material is upgraded to premium product using pelletization.