New Mexico Mineral Symposium — Abstracts

Those of us who are living in central—north-central New Mexico and those of you from the other regions of New Mexico and other states have enjoyed "going up the Pecos" for many years. Whether you picnicked with family on holidays in the 50s, fly fished in the Pecos all years, or hiked in the Pecos Wilderness, we all have enjoyed "getting out" and seeing the colors in the canyons.

If you were interested in old mine dumps and pyrite cubes then you played on the dumps of the above mine, which was often called "Tererro mine." The mine was very clearly visible on the then dirt road leading to Cowles. All of this has changed and is still changing. The road is now paved, the canyons and meadows are filling with log homes, and the dumps of an old famous mine are coming down.

Location
The Hamilton mine (and other names) is located in the Willow Creek district, San Miguel County, northeast of Santa Fe some 17 mi via 1-25 taking the Glorieta—Pecos exit into the town of Pecos. At Pecos turn left 13 mi past the Benedictine Monastery, Monastery Lake, and the New Mexico Department of Game and Fish hatchery to eventually start the hill climb at the Tererro general store and post office (second one, original was at the mining camp), and then after an additional 1.6 mi farther you start seeing the old mining dumps. At an elevation of 8,000 ft and sandwiched between towering cliffs of pink and brown granite, one truly enjoys "getting out."

History
The "Tererro mine," as it is sometimes known ("Tererro" is a corruption or misspelling of the Spanish word "terrero" meaning mound, dump, place for mine waste), had other names in its short history. Several sources report knowledge of the zinc-lead-copper deposits being worked in the 1880s. In 1881 the Pecos ore body was discovered by a prospector named Case. He apparently sold out, as at that time the deposits were referred to as "Hamilton" or "Cowles" mine of the Pecos Copper Company, A.H. Cowles being the name of the principal owner of the company. Small amounts of copper ore were mined and hauled by wagon to Glorieta where it was shipped by rail to El Paso for smelting. Goodrich—Lockhart Company acquired the mine in 1916. Large-scale mining did not start until 1925 when the American Metal Company (American Metal Climax, now Cyprus—Amax) took over. A 600-ton flotation mill, "El Molino," was built 12 mi to the southwest in Los Alamitos Canyon. Ore was transported via aerial tramway some 1,000 ft above the valley floor. The tram was reported to be the longest aerial tram in North America. For shipping of the concentrate, the railroad built a spur from the mainline into the mill. It was later reported that when the reclamation of the mill site was done there was no trace of the railroad spur (E. Duran, pers. comm. 1999). Lead, zinc, copper, gold, and silver ore production amounted to 700 tons a day valued at 40 million dollars. Rich ore contained 16% zinc, 4% lead, 1% copper, 3 oz of silver/ton, and 0.1 g of gold/ton. Total ore mined and milled for the entire period of operation exceeded 1.5 million tons. The mine operated successfully from 1929 to 1939 with occasional disruptions of water in tunnels and labor dissatisfaction. The mine had an ongoing employment of over 700 men and was considered the largest mine in terms of payroll in New Mexico. Work was in progress 7 days a week, 16 hrs a day with shift alternation. It supported a bustling camp of over 3,000 people, 200 homes, mine buildings, two stores, first post office, hospital, boarding house, school, teacher's apartments, a bunkhouse, a nine-hole golf course, and a professional baseball team.

Geology
A strange arrangement (my term) of sediment from ancient seas compacted to form shales and siltstone and mixed at the surface with volcanic flows and intrusive igneous rocks. Rock formation is dated at Precambrian. The rocks later underwent compressive movement crumpling the rocks into tightly compressed folds during mountain building. Extreme heat and pressure recrystallized the sedimentary and igneous rocks into metamorphic equivalents such as quartzite, mica, schist, and phyllites. At the Pecos mine site the prevailing rock is an amphibolite with biotite-hornblende, along with feldspar and pyrite present in granular form. The ore deposits formed a zone 60 ft wide in this amphibolite changing it to a chloritic schist containing biotite and tourmaline along with pyrite, chalcopyrite, and sphalerite.

The first tunnel was cut at the level of Willow Creek, and an 1,800-ft shaft put in later extended to 400 ft. Copper ore grading 17% was mined from this shaft. In 1925 when American Metal Company took over, two additional shafts, the Katydid and the Evangeline, were put down at two separate ore zones, one more than 1,000 ft.

Mineralogy
According to Northrop's Minerals of New Mexico, 1944 and 1959 revised editions and the 1996 edition revised by Florence LaBruzza, some 41 minerals could be found in the Willow Creek district.
They include:
 

Mining
No further mining of the ore bodies has taken place since 1939. Lease rights exist with Cyprus—Amax Minerals of Englewood, Colorado. They are administered by and access is controlled by both the mining company and the New Mexico Department of Game and Fish (J.W. Greene, Cyprus—Amax, and J. Pederson, NM Dept. Game and Fish, pers. comm. 1999). The mine site in fenced and posted against "trespassing, safety hazards, open mine shafts, unstable material, hazardous substances, and unsafe drinking water." In 1998, Duran Sand and Gravel of Pecos was awarded a contract (1999-2000) by Cyprus—Amax under authority of NMDG&F (Abandoned Mines Act) to "reclaim and restore to near natural state as possible" the El Molino mill in Los Alamitos Canyon. The mill buildings, tram, and buildings at the mine were razed according to lease in 1939. In 1999 the reclamation is complete for the mill site with burying of waste some 60 ft, leveling of hill where mill building sloped, total reseeding with native grasses and flowers, and creation of wet lands. The 1998 Reclamation Award was given to Cyprus—Amax for this project, and, as of this symposium, reclamation of large magnitude is underway on the old mine site.

Acknowledgments
The writers wish to thank Johnnie Greene of the Environmental Affairs Division, Cyprus—Amax Minerals Company, Englewood, Colorado, and Jeff Pederson of the Conservation Division, New Mexico Department of Game and Fish, Santa Fe, New Mexico for permission to access the mine and mill sites. Thank you to Mike Ellis of Cyprus—Amax and Eddie Duran of Duran Sand and Gravel, Pecos, New Mexico, for permission to use pictures of the old camp; to a friend of recent years, Virgil Lueth, Mineralogist and Curator of the New Mexico Bureau of Mines Mineral Museum, for microphotography of minerals and talking me through the geology; to my wife, Diane, for accompanying me at the mine, taking photographs, and occasionally administering first aid; and to a friend for 30 yrs, Bob Eveleth, Senior Mining Engineer of the New Mexico Bureau of Mines, for taking busy time to explain mining and milling processes.

References:

1. Northrop, S. A., 1944, 1959, Minerals of New Mexico: University of New Mexico Press, Albuquerque, New Mexico, 665 pp.
2. Northrop, S. A., and LaBruzza, F. A., 1996, Minerals of New Mexico: University of New Mexico Press, Albuquerque, New Mexico, 346 pp.