New Mexico Geological Society Annual Spring Meeting — Abstracts

The St. Cloud and U.S. Treasury Mines are located within the Chloride Mining District, situated along the eastern flank of the Black Range in Sierra County, New Mexico. The district consists of precious and base metal bearing epithermal fissure veins, hosted primarily by intermediate
volcanic and volcaniclastic rocks of the mid-Tertiary Datil-Mogollon volcanic field. The St. Cloud-U.S. Treasury vein has system a mineralized
strike length of approximately 7,700 feet; trends from N 45° W to N 70° W, and dips from 65° to 85° to the southwest. Ore grade mineralization occurs in distinct shoots within the vein system; with low grade to barren vein material surrounding the ore shoots. Recognized ore controls are primarily structural. The mineralogy of the ore shoots consists of bornite, sphalerite, galena, chalcocite, betekhtinite (Cu₁₀ (Fe,Pb)₆S₆) and chalcopyrite, with minor hematite, covellite, malachite, native silver and gold. Gangue mineralogy consists of quartz, calcite, and minor adularia (sericite).