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A History of Mineral Collecting at the Chino Mine

Grant County, New Mexico



The Chino mine is probably one of the oldest collecting sites in North America. A copper bell, dated ca. 1150, has been excavated from a nearby Mogollon site.* Though yet to be studied in detail by archeological scholars, Chino copper and turquoise doubtless have been collected at the site since prehistoric time. The mine derives its name from the Spanish term for chalcopyrite (formally, copper pyrite), not as an allusion to the Chinese, as has long been reported.


*The Mogollon (named after the mountain range in southwestern New Mexico) were an ancient Native American group that inhabited the area and built the structures at the Gila Cliff Dwellings National Monument around Silver City. They abandoned the region, much like the Anazazi left the Four Corners, around 1400. The Apache later moved into the area and made it their homeland.


The Chino mine is located in eastern Grant County, New Mexico, approximately 12 miles east of Silver City, the county seat. The town of Santa Rita, once nearly surrounded by the mine (hence the name Townsite Island on many mine maps), served for many years as the center of mining activity until it was completely engulfed by the open pit in the 1970s. The deposit is often referred to as the Santa Rita deposit, or some reference is made to the former town, in geological literature.


Mining has progressed nearly continuously in the area of the Chino mine for more than the past two hundred years and is still active today. From 1911 to 2006, the mine produced more than 5.9 million tons of copper and 500,000 ounces of gold (McLemore 2008). Chino was the fifth- largest copper producer in the United States in 2005, producing 104,800 tons. Although production dropped to 92,900 tons in 2006, the mine rose to third in U.S. production for the year (Phelps Dodge, company annual reports). Chino Mines Company, a wholly owned subsidiary of Freeport McMoRan Copper and Gold, currently owns and operates the mine.

Figure 1. The Chino mine in September 2006. Gibbs photo.

Figure 1. The Chino mine in September 2006. Gibbs photo.


Collecting of mineral specimens has been continuous for many years, with punctuated finds of minerals of significant interest to collectors throughout the mine's history. Native copper and cuprite specimens are best known, but interesting phosphate minerals, including beautiful blue turquoise, have also been collected. Specimens of secondary copper minerals, such as azurite and malachite, are rarely seen in modern collections.


GEOLOGY
The Chino (Santa Rita) deposit is a porphyry copper orebody that includes intrusive- and skarn-hosted copper mineralization. Chino is located in a complex geological setting (fig. 2) in the transition zone between the Colorado Plateau and Basin and Range physiographic provinces (Jones, Herndon, and Moore 1967). Early Tertiary mineralization is associated with a porphyritic composite intrusive, varying in composition from granodiorite to quartz monzonite that has intruded and domed surrounding Paleozoic and Cretaceous sedimentary rocks (fig. 3). Sedimentary rocks in the district include Paleozoic and Upper Cretaceous sandstone, limestone, dolomite, and shale. Late Cretaceous quartz diorite sills that predate the main stock intrusive but are not believed to be associated with mineralization also intruded the sedimentary section. Three types of dikes—granodiorite, quartz monzonite, and quartz latite—of different ages cut the intrusive (Neilson 1968). The latite dikes are unmineralized, and the quartz monzonite types are only rarely mineralized (but seldom of ore grade). The granodiorite dikes are occasionally mineralized. Postmineral (mid-Tertiary) rhyolitic volcanic rocks overlie the southern and southeastern portion of the deposit. These rocks, which were extruded about 35 million years ago (Ma), include the Sugarlump and “Kneeling Nun” tuffs and probably overlaid the entire deposit at one time. These tuffs are overlain, in places, by basaltic andesite flows. Subsequent weathering has exposed the porphyry system and left remnants of the tuffs that comprise the famous Kneeling Nun landmark that resides on the southeast side of the mine.

Figure 2. Physiographic map of New Mexico showing the location of the Chino mine.

Figure 2. Physiographic map of New Mexico showing the location of the Chino mine.


Hydrothermal alteration and mineralization are associated with the intrusion of the Santa Rita composite stock, which has been dated by 40Ar/39Ar methods at between 58.1 and 59 Ma. The stock was intruded at the junction of three sets of faults, including pronounced northwest and northeast sets and a less prominent easterly set. The intrusion is elongate in a northwest-southeast direction. Abundant mineralized fractures show the stock was intensively fractured closely following solidification and attending hydrothermal alteration. Nonskarn alteration includes potassium feldspar, biotite, quartz-sericite-pyrite, and argillic alteration. Pennsylvanian and Mississippian sedimentary rocks, primarily limestone, that were invaded by the magma were completely altered and replaced by calc-silicates and associated contact-metasomatic minerals (Nielson 1970). Common skarn minerals include magnetite, pyrite, quartz, andradite, epidote, actinolite, chalcopyrite, ilvaite, and others in lesser amounts. The distribution of the skarn minerals is generally controlled by their proximity to the stock. However, some, such as magnetite, are also controlled laterally by the composition of the Paleozoic host rocks (Lueth 1996). Skarn minerals at Chino are typically massive and often altered, diminishing their specimen value.

Figure 3. Geologic cross section of the Chino mine, looking north. Standard geologic age abbreviations are keyed to rock symbols.

Figure 3. Geologic cross section of the Chino mine, looking north. Standard geologic age abbreviations are keyed to rock symbols.

Figure 4. Remains of the old Spanish fort at Santa Rita, ca. 1910. The fort is the round building to the left of the larger rectangular building. The famous landmark known as the “Kneeling Nun” is located on the end of the ridge but is obscured due to the angle of the photo. The current open pit extends to the base of the cliff in the photograph. NMBGMR photo archives SH00296.


Figure 4. Remains of the old Spanish fort at Santa Rita, ca. 1910. The fort is the round building to the left of the larger rectangular building. The famous landmark known as the “Kneeling Nun” is located on the end of the ridge but is obscured due to the angle of the photo. The current open pit extends to the base of the cliff in the photograph. NMBGMR photo archives SH00296.


Chalcopyrite is the primary hypogene copper mineral in both skarn and unenriched intrusive rocks. Without secondary chalcocite enrichment, however, little other than the skarns would be of ore grade. Cretaceous clastic sedimentary rocks, and the quartz diorite porphyry sills within surrounding sedimentary rocks, are also secondarily enriched, frequently to ore grade. The upper Paleozoic rocks, though extensively altered by skarn mineralization, were not as reactive to descending supergene solutions and, consequently, were not greatly susceptible to secondary enrichment. Subsequent oxidation of the chalcocite-enrichment blanket has resulted in the formation of some of the better-known copper minerals in the deposit, including native copper, cuprite, libethenite, and turquoise.


EARLIEST DISCOVERY AND COLLECTING
The occurrence of native copper at Santa Rita resulted in some of the earliest mining in the Southwest. Records indicate that Spanish explorers came north from Mexico to explore the area, beginning with Don Juan de Oñate in 1598. The exact time when the Spanish gained knowledge of the deposit is unknown, but ca. 1795 Capt. Francisco Martínez, stationed at El Presidio de Carizal, mentions El Cobre near Santa Lucia Springs as a criadero. A criadero or nursery (where minerals “grow”) was at the time considered a natural wonder, with such occurrences of metals reserved for the Spanish Crown. Consequently, there was little incentive to develop such deposits of native metal “growing” from the soil until Jose Manuel Carrasco, a soldier stationed about 150 miles south of Santa Rita at El Presidio de Janos, took the initiative to develop the deposit in the early nineteenth century. By about 1801 Carrasco had interested his friend Don Francisco Manuel Elguea, a wealthy and influential merchant from Chihuahua, in Santa Rita copper, resulting in contracts to supply copper for Mexican coinage by 1804 (Christiansen 1974). Sheets of native copper were sent from Chino on the backs of donkeys and mules over 300 miles of desert landscape to the city of Chihuahua.


NATIVE COPPER

Native copper is common in the oxidation zone of porphyry copper deposits, typically forming near the top of chalcocite enrichment. Here, copper in chalcocite is reduced to the native state with accompanying oxidation of sulfur to sulfate, as suggested by Lindgren from observation of Morenci ore, by the following reaction:


Cu+12S + 3Fe+32(SO4)3+ 4H2O = Cu0 + 6Fe+2SO4 + 4H2SO4.


Even though ferric iron is responsible for the oxidation of chalcocite in this geologic setting, little hematite is present that is associated with native copper in recent finds at Chino, perhaps due to the relatively low pyrite content in this area of the pit. Much of the native copper at Chino occurs in the Santa Rita granodiorite stock to the west and beneath retrograde skarn mineralization in a “roof pendant” in the East pit area of the mine. Shiny, flattened specimens were collected in 1998 from fractures in skarn hosted by the Syrena Formation, suggesting that a change in pH rather than Eh (oxidation potential) is responsible for the deposition of native copper from solution.

Figure 5. Flattened crystals of copper extracted from fractures, the most common form in the NMBGMR Museum. Specimen is 8 cm across. Specimen 75, C. T. Brown collection; Virgil Lueth photo.


Figure 5. Flattened crystals of copper extracted from fractures, the most common form in the NMBGMR Museum. Specimen is 8 cm across. Specimen 75, C. T. Brown collection; Virgil Lueth photo.


The best specimens occur in the stock, and in some of the most recent finds they are intimately associated with alunite. Associated minerals with the native copper include quartz, sericite, and minor orthoclase. Pyrite and hematite are present but in relatively small amounts.


Well-formed pyritohedra of pyrite were found in occasional sericite veins. It has been reported that one specimen was the size of a baseball, although most are less than 4 cm across. Some of these well-formed pyrites are coated with chalcocite, producing classic pyritohedral “ducktownites” (chalcocite coatings, of variable thickness, on pyrite similar to those seen at Ducktown, Tennessee; hence, the name ducktownite). Djurleite coatings on these pyrite crystals have also been reported (Northrop and LaBruzza 1996), but we know of no analytical data that confirm the presence of the species.

Figure 6. Pyrite coated with chalcocite in sericite, otherwise known as “ducktownite.” Largest crystal is approximately 2.5 cm. Ray DeMark specimen, Jeff Scovil photo.

Figure 6. Pyrite coated with chalcocite in sericite, otherwise known as “ducktownite.” Largest crystal is approximately 2.5 cm. Ray DeMark specimen, Jeff Scovil photo.


Cuprite is often found as an oxidation product on the native copper as coatings and in crystalline form as cubes, octahedra, and dodecahedra. Native copper has also been found recently in the South pit area of the Chino mine as finely crystalline masses in fractures associated with chrysocolla and the chalcotrichite variety of cuprite.


Fine specimens of copper and cuprite in combination have been produced from the Chino mine for many years. The New Mexico Bureau of Geology and Mineral Resources (NMBGMR) Mineral Museum in Socorro contains specimens from at least as far back as the early part of this century (C. T. Brown collection). Some of the earliest specimen numbers in the NMBGMR collections are copper specimens from Chino (fig. 5). Additions to the museum collection over time provide a chronology for the production of fine specimens from the mine. Typical ore samples of native metal in fractures hosted by granitic rock are most common. A few crystalline pieces are noted, some with morphologies similar to the most spectacular recent finds. Later specimens, often dominated by spinel and polycyclic twinning, were produced in the 1970s. Surprisingly, no copper specimens from Chino were advertised or mentioned in articles from The Mineral Collector (1894–1909) although the mine was active. Malachite and azurite were noted in articles and advertisements, but these species are now rarely seen.

Figure 7. Large cuprite crystal group from Chino. Largest crystal is approximately 2.4 cm. Ray DeMark specimen, Jeff Scovil photo.

Figure 7. Large cuprite crystal group from Chino. Largest crystal is approximately 2.4 cm. Ray DeMark specimen, Jeff Scovil photo.


Specimen-grade native copper and cuprite were extensively collected in late 1993 and early 1994, when numerous samples of coarsely crystalline copper with coatings of cubic cuprite crystals were encountered during mining in the East pit area of the mine. Many of these crystallized copper and cuprite specimens included some uncommon crystal habits for the deposit, including dodecahedral forms. A single boulder mined in March 2001 was recovered from an inactive concentrator stockpile that yielded some spectacular crystalline specimens sold in early 2002. Crystal forms include spinel twins, dodecahedra, and modified cubes. Often single specimens show differing crystal habits. Some finely crystalline copper “wool” occurred on some specimens as a secondary crystallization. Additionally, many good examples of crystalline copper of good quality were found in the area.

Figure 8. Polycyclic twin crystals of copper recovered in the 1970s. Specimen is 10 cm in long dimension. NMBGMR Museum specimen 16492, gift of James Eacret; Virgil Lueth photo.

Figure 8. Polycyclic twin crystals of copper recovered in the 1970s. Specimen is 10 cm in long dimension. NMBGMR Museum specimen 16492, gift of James Eacret; Virgil Lueth photo.


The main body of native copper mineralization in the East pit was first encountered at about 700 feet below the original land surface, at an elevation of 5,650 feet. The best specimens have been found sporadically between an elevation of about 5,500 feet and the current pit bottom on the 5,150 bench. Mining was stopped in 2001 about 50 feet above the bottom of the native zone that produced the most recent nicely crystallized specimens. Copper mineralization extends in an adjacent zone to about the 4,750-foot elevation, a total vertical extent of 900 feet, but current plans include mining only to the 5,000-foot elevation. Additional discoveries are anticipated when mining resumes.

Figure 9. Photomicrograph of cubic cuprite on dodecahedral copper with selenite. Field of view is 6 mm. Ray DeMark specimen, Virgil Lueth photo.

Figure 9. Photomicrograph of cubic cuprite on dodecahedral copper with selenite. Field of view is 6 mm. Ray DeMark specimen, Virgil Lueth photo.


Spinel Twins
 
Copper crystals as spinel twins have been found at Chino off and on for many years. One fine example is the copper specimen known as the “chili pepper,” currently in the collection of the NMBGMR Mineral Museum and used as the museum's “unofficial mascot.” More recently, in 2006, a spectacular find was made of complexly twinned copper crystals to 15 cm in length from the Townsite Island area of the Chino mine.

Figure 10. Copper from the 2001 find, illustrating the wide variety of crystal forms within a single specimen. Specimen is 10 cm. NMBGMR Museum specimen 16387, Jeff Scovil photo.


Figure 10. Copper from the 2001 find, illustrating the wide variety of crystal forms within a single specimen. Specimen is 10 cm. NMBGMR Museum specimen 16387, Jeff Scovil photo.

Figure 11. Copper “chile pepper,” the NMBGMR Museum's unofficial mascot (15352). Specimen is 9.5 cm long. It was collected in the 1960s and resided at the Royal Scepter Rock Shop in Silver City until 1994 when it was purchased by Ron Gibbs and later sold to the museum, Jeff Scovil photo.

Figure 11. Copper “chile pepper,” the NMBGMR Museum's unofficial mascot (15352). Specimen is 9.5 cm long. It was collected in the 1960s and resided at the Royal Scepter Rock Shop in Silver City until 1994 when it was purchased by Ron Gibbs and later sold to the museum, Jeff Scovil photo.


This portion of the mine was already well known for native copper specimens, typically as fracture fillings of leaf and arborescent crystallized copper, some more than 30 cm in size. The find in 2001 by Stan Esbenshade (of Tucson) resulted in the recovery of a number of fine crystallized copper specimens from a region between the Townsite Island area and the East pit area. Although these were not spinel twins, they were large specimens with well-developed crystals the size of walnuts.


In 2006, mining had progressed to the 5,200-foot level of the Townsite Island area of the mine when evidence of copper mineralization was noted. The initial specimens were chalcocite psuedomorphs after arborescent copper crystals; later, small specimens of massive vein fillings and crystalline copper began to appear. That year a number of large specimens of copper were found along with several smaller, well-crystallized specimens exhibiting spinel twinning. There was sufficient mineralization present for the Mimbres Mining Company (the contracted mineral recovery company) to mobilize a small excavator for a week of collecting. Many small and large specimens were recovered; the largest weighed approximately 350 pounds prior to cleaning.


In June 2006, miners noticed small crystalline copper specimens on the 5,150-foot level that turned out to be well-formed spinel twins. Further investigation led to the discovery of a well-defined zone or “vein” of intergrown arborescent copper. Esbenshade spent two days mining the zone and recovered several hundred doubly terminated spinel twins that ranged in size from less than 1 cm to more than 15 cm in length. Only so much collecting could be done by hand, and collecting with an excavator was planned after the initial batch of specimens was cleaned. Unfortunately, that area of the mine was allowed to flood, which eventually covered the deposit, preventing further collecting efforts, at least for now.


Figure 12. Herringbone-style crystals of copper from the 2001 find. Specimen is 12.5 cm across. NMBGMR Museum specimen 16593, Jeff Scovil photo.


Figure 12. Herringbone-style crystals of copper from the 2001 find. Specimen is 12.5 cm across. NMBGMR Museum specimen 16593, Jeff Scovil photo.


The spinel twins grew within a mass of loosely intergrown aborescent crystallized copper that formed almost a spongy mass. Vigorous shaking could loosen the whole mass, and it would disintegrate in one's hand. The twins grew within the mass but without attachment. They are readily removed from the enclosing crystalline copper without damage. As found, the crystals are a dark reddish-brown color, resulting from a layer of goethite growing over a thin coating of cuprite. Although various methods were tried for removing the goethite without damage to the cuprite, none was satisfactory, and the majority of the specimens were cleaned to remove both the goethite and the cuprite. The resulting bright coppery specimens will eventually regain a more subdued patina.

Figure 13. Spinel-twinned copper from the most recent (2006) find at the Chino mine. Specimen is 8 cm long. Jay Rosenbauer specimen, Ron Gibbs photo.

Figure 13. Spinel-twinned copper from the most recent (2006) find at the Chino mine. Specimen is 8 cm long. Jay Rosenbauer specimen, Ron Gibbs photo.


SECONDARY MINERALS
 
Interestingly, very few collectible minerals from the Chino mine, other than native copper, cuprite, and turquoise, are typically seen in collections today. A number of factors may contribute to this surprising lack of secondary copper minerals. Areas where secondary copper minerals such as azurite and malachite were deposited may have been relatively limited during the weathering history of the deposit. The presence of a thick limestone section on the north end of the pit suggests that they should have been more abundant. Perhaps the lack of copper secondary minerals is partly due to the long mining history at Chino. Mining through the oxidized capping was accomplished long ago, and many fine specimens may have been lost to history.

Figure 14. Single spinel-twinned copper crystal on copper “wool” matrix. Specimen is 7.5 cm in longest dimension. Jay Rosenbauer specimen, Jeff Scovil photo.


Figure 14. Single spinel-twinned copper crystal on copper “wool” matrix. Specimen is 7.5 cm in longest dimension. Jay Rosenbauer specimen, Jeff Scovil photo.


Phosphate Minerals
 
Like nearly all the porphyry copper deposits of the Southwest, the oxidized zone of the orebody at Chino contains a suite of secondary phosphate minerals. Careful collecting in these phosphate-rich zones has led to the discovery of a wide variety of less-well-known species for the mine, mostly as microminerals. Undoubtedly, a number of other species probably exist in these zones.


Apatite of a primary origin can be found as creamy white, elongated prisms associated with pyrite, muscovite, quartz, and calcite. These crystals can be several millimeters in length and were especially prominent in the Whim Hill breccia. Apatite of secondary origin is found in the oxidized zone as small, white, stout hexagonal prisms associated with libethenite and pseudomalachite.


Libethenite occurs most typically as lustrous, green, transparent, elongated prisms associated with pseudomalachite, apatite, and chrysocolla. It is found in the oxidized portion of the orebody.

Figure 15. Large spinel twin, 4 cm long, with its original patina of cuprite/goethite. Whole mass of “wool” is 18 × 18 × 5 cm and has several large spinel twins inside. Ron Gibbs specimen and photo.

Figure 15. Large spinel twin, 4 cm long, with its original patina of cuprite/goethite. Whole mass of “wool” is 18 × 18 × 5 cm and has several large spinel twins inside. Ron Gibbs specimen and photo.


Pseudomalachite is also restricted to the oxidized portion of the orebody and is associated with chrysocolla, apatite, and libethenite. It occurs as small, dark green, equant, minutely intergrown crystals and seldom as simple individual crystals. Often the groups of crystals resemble orbs and botryoidal clusters.

Figure 16. Rarely seen azurite-malachite-calcite specimen from the Chino mine. The date this specimen was collected is unknown. Specimen is 15 cm in long dimension. It was originally in the Royal Scepter Gem and Mineral Museum collection until 1994 when it was acquired by the NMBGMR Museum (specimen 12812), Jeff Scovil photo.

Figure 16. Rarely seen azurite-malachite-calcite specimen from the Chino mine. The date this specimen was collected is unknown. Specimen is 15 cm in long dimension. It was originally in the Royal Scepter Gem and Mineral Museum collection until 1994 when it was acquired by the NMBGMR Museum (specimen 12812), Jeff Scovil photo.


Turquoise has been found sporadically at Chino for many years. Much of it occurs as thin vein fillings of little commercial value; however, larger masses and nuggets of fine gem- quality turquoise have occasionally been found.


A unique assemblage of secondary iron phosphates was discovered in 1995. First noted by local collector Rod Woodcock, they were subsequently identified through the efforts of Dr. William “Bill” Wise and Dr. William Birch (Birch et al. 1996). What was initially thought to be cacoxenite, and then phosphofibrite, was determined to be a new species, meurigite. The species had been found in other locations; however, the material from Chino occurred as larger crystals, enabling the description of the species to be completed. The Santa Rita pit was noted as the type locality for meurigite. The mineral was found in fault gouge in the Townsite area of the mine. Specimens were recovered from freshly blasted material, and subsequent inspection of the area as mining continued failed to disclose any further occurrences.

Figure 17. Blocky white crystals of primary apatite with younger, elongated brown calcite. Apatite crystals are 2 mm long. Ron Gibbs specimen and photo.


Figure 17. Blocky white crystals of primary apatite with younger, elongated brown calcite. Apatite crystals are 2 mm long. Ron Gibbs specimen and photo.


Meurigite occurs as honey-yellow, tabular, elongated crystals forming spherical and hemispherical clusters growing on dufrenite. Individual crystals are rare. Meurigite is associated with dufrenite and beraunite.

Figure 18. Photomicrograph of typical clusters of elongated crystals of libethenite on brilliant white, equant tabular apatite crystals. Libethenite crystals are approximately 1 mm long. Ron Gibbs specimen and photo.


Figure 18. Photomicrograph of typical clusters of elongated crystals of libethenite on brilliant white, equant tabular apatite crystals. Libethenite crystals are approximately 1 mm long. Ron Gibbs specimen and photo.


Dufrenite occurs as minute, dark green, acicular crystals growing in radiating aggregates that are seldom more than 1 mm. They are differentiated from beraunite by their size and their satin luster.

Figure 19. A partially polished turquoise nugget from the Chino mine. Specimen is 12.5 cm long. NMBGMR Museum specimen 13119, gift of Don Moore; Virgil Lueth photo.


Figure 19. A partially polished turquoise nugget from the Chino mine. Specimen is 12.5 cm long. NMBGMR Museum specimen 13119, gift of Don Moore; Virgil Lueth photo.

Figure 20. Photomicrograph of tight clusters of thin tabular, golden meurigite on radiating aggregates of dark green, acicular beraunite. Clusters are about 1 mm across. Ron Gibbs photo and specimen.


Figure 20. Photomicrograph of tight clusters of thin tabular, golden meurigite on radiating aggregates of dark green, acicular beraunite. Clusters are about 1 mm across. Ron Gibbs photo and specimen.


Beraunite occurs as long, dark green, lustrous, acicular crystals forming flat radiating aggregates sometimes over 20 mm in diameter.


The collecting history of the Chino mine is much like that of many longtime specimen producers. The earliest collectors were native peoples who collected the material for utility or ornamentation. The Spanish/Mexican collectors focused on the large material for utility or coinage. As collecting has become more sophisticated, additional numbers of aesthetic pieces with variations in crystallography have become prevalent. In addition, as new species are discovered, they are added to collections. Throughout its long collecting history, Chino has produced a large number of exceptional mineral specimens. More fine pieces will probably come to light as long as mining continues at Chino, one of the oldest collecting localities in North America.

Figure 21. Photomicrograph of radiating clusters of elongate dufrenite crystals with small cluster of meurigite coating beraunite. Field of view is about 1 cm across. Ron Gibbs photo and specimen.

Figure 21. Photomicrograph of radiating clusters of elongate dufrenite crystals with small cluster of meurigite coating beraunite. Field of view is about 1 cm across. Ron Gibbs photo and specimen.


ACKNOWLEDGMENTS
We thank Ray DeMark for reviewing the manuscript and providing photographs for inclusion in the article. Robert Eveleth, John Rakovan, and Peter Modreski also reviewed the manuscript and provided suggestions for its improvement.


REFERENCES

1. Birch, W. D., Pring, A., Self, P. G., Gibbs, R. B., Keck, E., Jensen, M. C. and Foord, E. E. (1996) Meurigite, a new fibrous iron phosphate resembling kidwellite.. Mineralogical Magazine 60, pp. 787-93.

2. Christiansen, P. W. (1974) The story of mining in New Mexico, New Mexico Bureau of Geology and Mineral Resources scenic trips to the geologic past 12

3. Jones, W. R., Hernon, R. M. and Moore, S. L. (1967) General geology of the Santa Rita Quadrangle, Grant County, New Mexico, U.S. Geological Survey professional paper 555.

4. Lueth, V. W. (1996) Garnet resource potential in southern New Mexico, New Mexico Bureau of Geology and Mineral Resources bulletin 154.

5. McLemore, V. T. (2006) Chino mine, Santa Rita district, Grant County, New Mexico.. New Mexico Geological Society 59th Fall Field Conference guidebook, pp. 41-43.

6. Nielson, R. L. (1968) Hypogene texture and mineral zoning in a copper-bearing granodiorite porphyry stock, Santa Rita, New Mexico.. Economic Geology 63, pp. 37-50.

7. Nielson, R. L. (1970) Mineralization and alteration in calcareous rocks near the Santa Rita stock, New Mexico.. New Mexico Geological Society 21st Fall Field Conference guidebook, pp. 133-39.

8. Northrop, S. A. and LaBruzza, F. A. (1996) Minerals of New Mexico, 3rd ed., University of New Mexico Press, Albuquerque.


Dr. Virgil W. Lueth, a consulting editor of Rocks & Minerals, is the senior mineralogist/economic geologist and curator of the Mineral Museum at the New Mexico Bureau of Geology and Mineral Resources, Socorro, New Mexico.

   Ronald B. Gibbs is a senior engineer with Freeport-McMo-Ran Copper and Gold in Oro Valley, Arizona.

   Robert M. North is a senior consulting geologist for Freeport-McMoRan Copper and Gold in Oro Valley, Arizona..
   
    
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