New Mexico Mineral Symposium — Abstracts

The rare lead-iron silicate melanotekite was first found in Langban, Sweden, and described by G. Lindstrom (1880). C. H. Warren (1898) described melanotekite chemically and crystallographically from material that had been provided by George E. Robin from Hillsboro, New Mexico. The material was reported to have been from the Rex and Smuggler mines near Hillsboro. In November 1898, A. E. Foote of Philadelphia was offering melanotekite as "distinct crystals with massive material" for sale in the The Mineral Collector (1898). Subsequent to A. E. Foote's offering, early mineral dealers Otto Kuntze, Ray Hopping, and Lazard Cahn were also offering melanotekite from Hillsboro for sale in The Mineral Collector.

In May 1981, one of the authors (R. S. DeMark) collected some lustrous, black crystals from what was at that time an unknown mine, high on a bluff on the north side of Percha Creek, across from the Percha (S. J. Macy) mine. These crystals were identified as kentrolite by microprobe analysis by Paul Hlava (pers. comm. 1981). Paul gave a presentation on this material at the Third New Mexico Mineral Symposium in November 1982. The mine name still was unknown at that time.

In 1987, Vandal King gave the author (R. S. DeMark) a specimen with an old label that identified the material as melanotekite from Hillsboro, New Mexico. It was massive material in ferruginous jasperoid. A chip from this specimen was provided to Paul Hlava for microprobe analysis. It was confirmed to be melanotekite (Hlava, pers. comm. 1987). The specimen came from stock in Ward's Natural Science Establishment and was quite likely from George English's material that was sold to Ward's in 1905. A thorough search of the mine on the north bluff of Percha Creek provided material identical in appearance to the specimen provided by Vandal King.

According to Paul Pohwat (pers. comm. 2001), the national (Smithsonian) collection contains seven melanotekite specimens from Hillsboro, three from the Bosch collection (1880s-1920s), one from Frederick Canfield (1926), one from the Roebling collection (1926), and two others. Two specimens were X-rayed and two were micro-probed to establish identification. The Smithsonian collection also contains two kentrolite specimens, one was purchased from Arthur Montgomery in 1938 (not X-rayed), and one specimen from Howard Belsky, in 1938, also not X-rayed.

A search of historical claim records at the Sierra County courthouse in 2001 provided a wealth of information regarding claim ownership, and location of mines in the Las Animas district near Hillsboro. The unknown mine on the north bluff of Percha Creek was determined to be the Big Chief mine. It was located in June 1892 by three men (T. Nolan, D. Chandler, and E. H. Welch) and witnessed by Stephan Macy (2001). The mines from which melanotekite was first identified by Warren in 1898, were the Rex and Smuggler. The Rex mine was located in December 1896, and two of the claim owners were George Robin and S. J. Macy (2001). The Rex mine was partly located by a bearing line of N70° 55' to the highest peak of the Caballo Mountains. The Rex mine is positioned about 1 mi northwest of the Big Chief mine on Ready Pay gulch.

A thorough search of the dumps and the underground workings of the Rex mine did not turn up any material resembling the material (crystals or massive) of the identified melanotekite specimens provided by Vandal King or the kentrolite crystals identified by Paul Hlava from the Big Chief mine. The Smuggler mine is about 3 mi northeast of Hillsboro and is not considered a viable location for the melanotekite/kentrolite. Specimens collected from the dumps of the Big Chief mine by the authors in November 2010 were examined by (R. P. Richards) using EDS on a JEOL scanning electron microscope with INCA software. A few grains from the massive material and rare euhedral crystals were found to be Fe-dominant (melanotekite), whereas most of the black and reddish crystals were Mn-dominant (kentrolite). In one case, both minerals were found on the same crystal! There seems to be no physical characteristic that would allow visually distinguishing melanotekite from kentrolite.

One hundred thirteen years ago, C. H. Warren described melanotelcite provided by George Robin reputedly from the Rex and Smuggler mines. The mineralogy of these two mines does not support this contention. Material from the Big Chief mine matches chemically and crystallographically the material that Warren studied. We suggest that the original location of the Rex and Smuggler for melanotekite was a "red herring" to obfuscate the true Big Chief mine location, which was not under claim by George Robin. End of story?

References:

1. Foote, A. E., 1898, Inside front cover advertisement: The Mineral Collector, v. 5, n. 9.
2. G. Lindstrom, 1880, Ofv., AK. Stock., XXXX, no. 6, p. 53.
3. Sierra County Courthouse, Claim Records, Book E, p. 734.
4. Sierra County Courthouse, Claim Records, Book F, p. 537.
5. Warren, C. H., 1898, Mineralogical notes: 1-on the occurrences of melanotekite and kentrolite: American Journal of Science, series 4, v. 6, pp. 116-124.