New Mexico Geological Society Annual Spring Meeting — Abstracts

In 1992, New Mexico accounted for about 83% of domestic potash production and supplied about 27% of domestic consumption. The potash industry of New Mexico produces both sylvite (KCI) and langbeinite (K₂SO₄•2Mg(SO₄)₂) in various size grades and purities, as well as artificial K₂SO₄. Potash was discovered in southeast New Mexico in 1925 during oil dri1ling in Eddy County; six companies are now active in the Carlsbad Potash District (Known Potash Leasing Area or KPLA) which is administered by the BLM. Average ore grade of sylvite in New Mexico has decreased from 25-30 K₂O equiv. wt % in the 1950's to about 14% today. Langbeinite ore now averages 8-10 K₂O equiv. wt %. Ore reserves of both types exist within the KPLA and should sustain production for 25 to 35 yrs.

Commercial potash occurs in the middle or McNutt Member of the Salado Formation of the Ochoan system (Upper Permian). The 590-ft-thick McNutt Member dips about one degree east and contains 11 of the 12 ore zones in the Salado, but only some of them are now economic. The zones are 3-10 ft thick and contain sylvite and langbeinite ore together with halite and accessory leonite, kainite, carnallite, polyhalite, kieserite, bloedite, anhydrite, and clay minerals. The zones are stratigraphically consistent, but are locally interrupted by barren halite (salt horses) formed later by migrating fluids.

Room-and-pillar mining, followed by pulling most of the pillars, is used with recovery of about 90% of the potash resource. Continuous-mining equipment adapted from the coal industry is used where the ore is soft. Harder ore, particularly containing langbeinite, requires mechanical undercutters, drilling, and blasting. Thin ore is sometimes mined with boring machines. Beneficiation is by flotation, crystallization, or both. The mineralogy and proportion of clay minerals, which may be up to 7% of the ore, influence optimum milling procedures and acceptable ore grade.

Other industries affect the production of potash in southeastern New Mexico. Oil companies compete for land use over deeper petroleum pools, and the Waste Isolation Pilot Project (WIPP) has led to withdrawal of land containing minable potash. Although potash deposits extend outside of the KPLA, none are economic at present. Development of low-cost potash in other parts of the world or changes in taxes, tariffs, or agricultural/fertilizer usage, would drastically affect the New Mexico potash industry.