Famous Mineral Localities: The Erupcion/Ahumada Mine: Los Lamentos District Chihuahua, Mexico

The next section of the manto extends from the Nuevo Mundo Fault to the San Luis Fault, a distance of 170 meters, and includes the Cueva Nuevo Mundo, then the Cueva de la Cruz, the sub-manto 5-14 Cave, and the Long Tom Cave. The first of these has an irregular roof extending to over 150 feet in height, and measures 300 feet wide and 500 feet long (covering approximately the area of two football fields!). The northern (lower) end connects with the tortuous, 100-meter Long Tom Cave. just before the San Luis Fault is the Las Gâteras ("The Gutters") glory hole where the first strong wulfenite mineralization occurs; many fine caramel-colored cubes on white botryoidal calcite were collected here.

At the San Luis Fault zone the manto expands into the Hojas de Plata Cave, a rather narrow 110-meter cavern ranging from 10 to 20 meters in width. The height decreases from 40 meters downward to about 5 meters at its lower end. The general trend of the cave descends to a lower limestone horizon around the SonoraVanadium Fault zone. A sub-manto ore channel is also associated here.

The wide Sonora-Vanadium Fault zone marks a physical shift in the orebody toward the west, and also carries intense wulfenite and vanadinite mineralization. At the 5th level, in the Ahumada portion of the workings, the wulfenite, vanadinite and descloizite begin to appear in abundance, and these minerals formed a significant portion of the ore on the 7th level (just above the water table). Several slopes were worked almost entirely in loose, spongy masses of acicular, dark brown, slightly arsenian vanadinite averaging 65% lead and 12% vanadium oxide. Below the 7th level the ore consisted of a mixture of cerussite, wulfenite, vanadinite and descloizite crystals. Scattered pipes and nests of wulfenite were found in other nearby slopes as well. In summary, it is safe to say lhat all wulfenite in collections today came from lhe Ahumada mine portion of the workings, belween lhe 500 and 720 levels, and none from lhe higher Erupcion mine workings.

North of the Sonora-Vanadium Faull a cavern called Los Banos ("The Balhs") was encountered, and in these workings, al the deepesl extension of the mine just above the water lable, the very finest wulfenite specimens were found, showing beautiful transparenl crystals wilh high luster.

The wulfenite and vanadinite mineralization seems to continue well below the water table, and in periods during which the water level has fallen, collectors have been able to remove significant quantities of fine specimens.

Below the Los Banos slopes at the 700 level the orebody plunges beneath the water table and has not been pursued further. A crosscut on the 800 level was started but had to be abandoned before reaching the manto. However, exploratory drilling in 1983 by the Penoles Exploration Company (in partnership with American Metal Climax) has revealed that the oxidation zone and its attendant secondary minerals extends for at least 250 more meters down the irregularly shaped manto to a depth of at least 80 meters below the current water table, and contains a modest reserve of ore. The drilling failed to locate an ore chimney, which is presumed to be situated even farther down-dip. Though insufficiently rich to justify renewed mining for lead, this 250 meters of manto below the water table very likely contains a wealth of mineral specimens. In fact, it was the pumping necessitated by the brief exploration work in 1983 that provided access to the 700 level for the first time in 20 years resulting in a fabulous find of wulfenite in the Los Banos slope. This slope is also heavily mineralized with vanadinite, which coats the walls.