New Mexico Mineral Symposium — Abstracts

Most New Mexican mineral collectors familiar with the zeolite minerals found in basaltic andesites near the Gila Cliff Dwellings can name several species easily. However, the exact species names were disrupted about 20 yrs ago when the zeolite group minerals received some serious nomenclature changes. For instance, "chabazite" is now divided into "chabazite-Ca," "chabazite-K," "chabazite-Na," and even "chabazite-Sr." Similarly, five species ending with Ba, Ca, K, Na, and Sr, depending upon the dominant cation, now represent "heulandite." This nomenclature change has left many a collector and museum curator in the lurch, not knowing what species they might have and causing headaches regarding analyzing, labeling, cataloging, etc. The identification of Gila zeolites also presented this challenge.

Zeolites found at the Grapevine campground on the East Fork of the Gila River, Grant County, recently analyzed by Tony Kampf using powder diffraction and EDS (on two specimens) have been further delineated. All of the tested East Fork zeolites have been Ca dominant. These include chabazite-Ca, heulandite-Ca, phillipsite-Ca, and lévyne-Ca. Note that lévyne, both Ca and Na, had an additional nomenclature change after the above mentioned zeolite nomenclature changes. Lévyne now has an accent! Stilbite, observed but not tested, could easily be assumed to be Ca-dominant as well. Other observed East Fork minerals are analcime, mesolite, calcite (rounded/weathered crystals up to 2 inches), quartz (usually as microscopic crystals showing multiple tapers, reverse scepters, and pagodas), a tiny late brown/black dendritic mineral (probably goethite) and late crusts and acicular crystals of a carbonate (perhaps aragonite). Of note were chabazite-Ca crystals reaching 1 inch.

Zeolites collected on the Middle Fork of the Gila River in Catron County have not been tested. Hopefully, they will have been analyzed by the 2011 New Mexico Mineral Symposium. If so, the results will be presented at that time. Minerals observed from the Middle Fork include "chabazite" (including variety phacolite), "heulandite," "stilbite," quartz, calcite, and a tiny fibrous, silky-lustered mineral with curved crystals resembling mordenite. The Middle Fork zeolites should be Ca-dominant. This is logical as Ca-dominant zeolites appear to be the most common worldwide.

Zeolites, quartz, and other species also occur on the trails leading to the Gila Cliff Dwellings.

The most common zeolites in the Gila area are heulandite-Ca and chabazite-Ca. Analcime and stilbite-Ca are also easily found, although the stilbite-Ca appears to be more localized. Mesolite, although a bit more rare, is locally common. Lévyne-Ca appears sparsely as white hexagonal wafers up to 1/4 inch, and one boulder had common colorless, gemmy, stubby, microscopic crystals. Notably, the same boulder contained a few phillipsite-Ca crystals.

The areas investigated for specimens were limited to the vicinity of the Grapevine campground (where the East Fork of the Gila River joins the West Fork), the adjacent SA Canyon and the Middle Fork area within 1 mi of the trailhead. Certainly, numerous other less accessible areas will likely produce interesting zeolites in the future.

Acknowledgments
Many thanks go to Tony Kampf for his recurring analytical help. And to Paulina Inigo for making this abstract sound less amateurish.