New Mexico Mineral Symposium — Abstracts

The best known pegmatite in New Mexico is the Harding pegmatite dike, well exposed in mine workings east of Dixon, Taos County. Once owned by Dr. Arthur Montgomery and subsequently donated to the University of New Mexico, it was mined over the years for lithium (lepidolite and spodumene), tantalum (microlite and columbite-tantalite), and beryl, (some of which is pink beryl rich in alkali metals and H₂O). Other distinctive minerals found at the Harding mine include manganese-bearing "rose" muscovite, albite variety cleavelandite, fluorapatite, eucryptite, bityite, holmquistite, and many more. Montgomery (1951) gave an interesting and classic account of the beryl mining, in which three men and a mule produced several hundred tons of hand-sorted beryl per year. Good summaries of the geology and mineralogy of the pegmatite were published by Jahns and Ewing (1976, 1977) and Brookins et al. (1979). Spilde (1999) described its bismuth carbonate and related minerals; see also Northrop (1959), Hlava (1979), and Modreski (1991). A comprehensive web page about the Harding pegmatite, including a complete bibliography and instructions for visiting the mine, is on the University of New Mexico Web site at http://epswww.unm.edu/harding/harding.htm .

West of the Rio Grande, the Petaca and Ojo Caliente pegmatite districts have been mined for muscovite mica and niobium-tantalum minerals (Jahns 1946, 1974; Holmquist 1947). The Globe pegmatite (Wright 1948) is one of the best known. Mangancolumbite at the Globe mine occurs in two forms, large blocky crystals and dendritic "feather" columbite, latter having formed within replacement pods of lamellar white albite (variety cleavelandite); other minerals include monazite as large brown crystals, green fluorite (with distinct white fluorescence under shortwave ultraviolet due to its high rare-earth content), and beryl (Jahns 1946; Northrop 1959; Hlava 1979). Similar minerals have been found at the Apache, Coats, Cribbenville, Fridlund, Star, and other pegmatite mines in these districts.

Several pegmatite districts on the east side of the Sangre de Cristo Mountains, including the Rociada, South Mora, Old Priest, and Elk Mountain districts, have been mined for mica, beryl, and tantalum (Redmon 1961; Holmquist 1946; Jahns 1946). The Rociada district is probably the best known of these to collectors, for its lepidolite, topaz, microlite, beryl, and other minerals (Sheffer and Goldsmith 1969; Jacobson 1987).

In recent years a number of other pegmatites occurring locally in northern New Mexico have produced minerals, often in well-crystallized form, including beryl, chrysoberyl, gahnite, titanite, epidote, margarite, and schorl, thanks to the diligent efforts of astute and observant collectors such as Ramon DeMark, Jesse Kline, and others.

An unusual pegmatite occurrence is the moonstone deposit at Rabb Park, Grant County, New Mexico. The moonstone (sanidine) occurs in pegmatite with associated aplite that is interpreted to have been partially crystallized pegmatite magma that was erupted and rapidly cooled (O'Brient 1986; see also Kelley and Branson 1947; Beard 2001).

Pegmatites in Rock Springs Canyon in the Organ Mountains have been mined in recent years for their minerals of interest to collectors, including orthoclase, albite, fluorapatite, smoky quartz, and titanite (Cowan 1994). Perhaps the most distinctive specimens from this area have been large crystals of orthoclase with oriented overgrowths of snow-white albite crystals. The large and euhedral, prismatic, fluorapatite crystals, as well as the associated titanite, greatly resemble the mineral assemblage found at the Crystal Lode pegmatite in Eagle County, Colorado (Young and Munson 1966).

References:

1. Beard, R., 2001, New Mexico moonstone; the Rabb Park deposit is a classic source of this feldspar gemstone: Rock & Gem, v.31, no. 6, pp. 20-24.
2. Brookins, D. G., Chakournakos, B. C., Cook, C. W., Ewing, R. C., Landis, G. P., and Register, M. E., 1979, The Harding pegmatite: summary of recent research; in Ingersoll, R. V., and Woodward, L. A. (eds.), Santa Fe country: New Mexico Geological Society, Guidebook 30, pp. 127-133. Cowan, C., 1994, Notable miarolitics of the Organ Mountains (abs): New Mexico Geology, v. 16, no. 1, p. 15.
3. Hlava, P. F., 1979, Microprobe analyses of columbites and tantalites from the Globe and Harding mines (abs.): New Mexico Minerals Symposium, University of New Mexico, Albuquerque, p. 6.
4. Holmquist, R. J., 1946, Exploration of the Elk Mountain mica deposits, San Miguel County, New Mexico: US. Bureau of Mines, Report of Investigations 3921, 7 pp.
5. Holmquist, R. J., 1947, Apache mica mine, Rio Arriba County, New Mexico: U.S. Bureau of Mines, Report of Investigations 4037, 5 pp.
6. Jacobson, M. I.,1987, The Pidlite pegmatite and other lithium-bearing pegmatites, Rociada district, San Miguel and Mora Counties, New Mexico: Mineral News, v. 3, no. 8, pp. 4-5.
7. Jahns, R. H., 1946, Mica deposits of the Petaca district, Rio Arriba County, New Mexico, with brief descriptions of the Ojo Caliente district, Rio Arriba County and the Elk Mountain district, San Miguel County: New Mexico State Bureau of Mines and Mineral Resources, Bulletin 25, 294
8. Jahns, R. H., 1974, Structural and petrogenetic relationships of pegmatites in the Petaca district, New Mexico; in Siemers, C. T., Woodward, L. A, and Callender, F. F. (eds.), Ghost Ranch: New Mexico Geological Society, Guidebook 25, pp. 371-375.
9. Jahns, R. H., and Ewing, R. C., 1976, The Harding mine, Taos County, New Mexico; in Ewing, R. C., and Kues, B. S. (eds.), Vermejo Park: New Mexico Geological Society, Guidebook 27, pp. 263??276.
10. Jahns, R. H., and Ewing, R. C., 1977, The Harding mine, Taos County, New Mexico: Mineralogical Record, v. 8, pp. 115-126.
11. Kelley, V. C., and Branson, 0. T., 1947, Shallow, high-temperature pegmatites, Grant County, New Mexico: Economic Geology, v. 42, no. 8, pp. 699-712.
12. Modreski, P. J., 1991, Pink and violet micas-composition, nomenclature, and genesis of muscovite and lepidolite micas from pegmatites and metamorphic rocks in northern New Mexico and central Colorado (abs.): New Mexico Geology, v. 13, no. 2, p. 41.
13. Montgomery, A., 1951, The Harding pegmatite-remarkable storehouse of massive white beryl: Mining World, v. 13, pp. 32-35.
14. Northrop, S. A., 1959, Minerals of New Mexico, revised edition: University of New Mexico Press, Albuquerque, 665 pp.
15. O'Brient, J. D., 1986, Preservation of primary magmatic features in subvolcanic pegmatites, aplites, and granite from Rabb Park, New Mexico: American Mineralogist, v. 71, no. 3-4, pp. 608-624. Redmon, D. E., 1961, Reconnaissance of selected pegmatite districts in north-central New Mexico: U.S. Bureau of Mines, Information Circular 8012, 79 pp.
16. Sheffer, H. W., and Goldsmith, L. A., 1969, Tantalum project, Rociada, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Mineral Resources Report 2, 15 pp.
17. Spilde, M., 1999, Bismuth minerals from the Harding mine; more than just yellow-green grunge (abs.): New Mexico Geology, v. 21, no. 1, p. 15.
18. Wright, L. A., 1948, The Globe pegmatite, Rio Arriba County, New Mexico: American Journal of Science, v. 246, pp. 665-688.
19. Young, E. J., and Munson, E. L., 1966, Fluor-chlor-oxy-apatite and sphene from Crystal Lode pegmatite near Eagle, Colorado: American Mineralogist, v. 51, no. 9-10, pp. 1476-1493.