New Mexico Mineral Symposium — Abstracts

The arsenate mineral carminite was first reported in New mexico from Granite Gap, Hidalgo County (DeMark, 1996). A new carminite occurrence has recently been discovered at Mine Hill in the Victorio Mountains, Luna County. Beudantite and adamite are also reported here for the first time from Mine Hill.

The Victorio Mountains are 18 mi west of Deming and easily accessible by leaving I—I0 at the Gage exit and driving about 3.5 mi south.
Mine Hill, at the southeast corner of the Victorio group, is composed mainly of faulted Silurian dolomite; the orebodies are deeply oxidized lead-zinc veins. It was the site of lead, zinc, silver, and gold mining from 1880 to the late 1950s. Total production for the entire period was less than two million dollars, over half of which was recovered during the first 25 years. Major producers were the Chance and Jessie claims; other important properties were the Rover, Rambler, Excess, and Helen claims. Ore minerals were listed by Griswold (1961) as cerussite, anglesite, silver halides, and native gold, with minor smithsonite and secondary copper minerals in a gangue of quartz, calcite, and various iron oxides. Lindgren, Graton, and Gordon (1910) observed that all the ores contained some arsenic.

Although Mine Hill has never been noted for mineral specimens, collectors have long known that microcrystals of secondary lead, zinc, and copper minerals occur there. The Helen yields cream, yellow, and orange mimetite and/or vanadinite; yellow to orange wulfenite; and occasionally square, orange to amber descloizite plates. Similar mimetite/vanadinite, as well as aurichalcite, malachite,
conichalcite, and sparse willemite have been found at the Rambler and the Excess. Cerussite and anglesite are uncommon except at the Rover, but they seldom form attractive crystals.
The newly discovered arsenates were all found on the Chance and Jessie dumps. Adamite occurs in fractures in pinkish-gray dolomite, associated with conichalcite and hemimorphite. Adamite forms sharp, lustrous, wedge-shaped microcrystals and rounded crystal aggregates that are colorless, pale blue, or bright turquoise blue. One sample of elongate, sea-green crystals was found. Adamite is nowhere abundant, most of the blue and green minerals on the dumps being aurichalcite and conichalcite. Conichalcite occurs as sprays of pale mint-green crystals, and as translucent apple-green to grass-green balls of dolomite and hematite.

Carminite and beudantite are usually found together, often accompanied by opaque white mimetite and occasionally by cerussite, in a quartz or hematite matrix. Beudantite forms yellow-green pods and streaks in the matrix, and tiny yellow crystalline masses. Carminite occurs as minute (<0.5 mm), lustrous, brilliant red, translucent crystals in single laths, radiating and bowtie sprays, and rounded clusters. In a single sample, abundant gray-green, amorphous bromargyrite is associated with carminite, mimetite, and beudantite. Late-stage calcite frequently permeates these rocks, partially filling pores and veinlets. Treatment with dilute HCl has produced mixed results.

One interesting sample from the Chance dumps displays quartz crystals associated with small rust-colored masses that are covered by a velvety reddish-brown outer layer, with carminite sprays and beudantite grains sprinkled over all. Preliminary microprobe analysis indicates that both the rust-colored material and the velvety material are calcium iron arsenates, tentatively identified as kolfanite [Ca₂Fe_³⁺3O₂(AsO₄)₃.2H₂O], and arseniosiderite [CaFe_³⁺3(AsO₄)₃ O₂.3H₂O] . If x-ray analysis confirms these identifications, two more arsenates will be added to the list of New Mexico minerals.

In 1994 the Abandoned Mine Land Bureau covered or backfilled all the Mine Hill shafts and adits, destroying the Helen, Rambler, and Excess dumps. Collecting is still possible on a few small ore piles near the Helen headframe and on the extensive, mostly undisturbed, Chance and Jessie dumps.

Acknowledgments—Special thanks to Arnold Hampson for color photomicrographs, to Paul Hlava for microprobe analysis and mineral identification, and to Mark Cunningham and the New Mexico State University SEM Laboratory for SEM photomicrographs.
 

References:

1. DeMark, Ramon, and Hlava, Paul, 1996, Carminite and other arsenates from Granite Gap, Hidalgo County, New Mexico: New Mexico Geology, v. 18, p. 19.
2. Griswold, G. B., 1961, Mineral deposits of Luna County, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Bulletin 72, pp. 69-86.
3. Lindgren, Waldemar, Graton, L. C., and Bordon, C. H., 1910, The ore deposits of New Mexico: U.S. Geological Survey, Professional Paper 68, pp. 285-295.