The Pyrochlore Supergroup of Minerals: Nomenclature

Abstract

A new scheme of nomenclature for the pyrochlore supergroup, approved by the CNMNC-IMA, is based on the ions at the A, B and Y sites. What has been referred to until now as the pyrochlore group should be referred to as the pyrochlore supergroup, and the subgroups should be changed to groups. Five groups are recommended, based on the atomic proportions of the B atoms Nb, Ta, Sb, Ti, and W. The recommended groups are pyrochlore, microlite, roméite, betafite, and elsmoreite, respectively. The new names are composed of two prefixes and one root name (identical to the name of the group). The first prefix refers to the dominant anion (or cation) of the dominant valence [or H 2 O or □] at the Y site. The second prefix refers to the dominant cation of the dominant valence [or H 2 O or □] at the A site. The prefix "keno-" represents "vacancy". Where the first and second prefixes are equal, then only one prefix is applied. Complete descriptions are missing for the majority of the pyrochlore-supergroup species. Only seven names refer to valid species on the grounds of their complete descriptions: oxycalciopyrochlore, hydropyrochlore, hydroxykenomicrolite, oxystannomicrolite, oxystibiomicrolite, hydroxycalcioroméite, and hydrokenoelsmoreite. Fluornatromicrolite is an IMA-approved mineral, but the complete description has not yet been published. The following 20 names refer to minerals that need to be completely described in order to be approved as valid species: hydroxycalciopyrochlore, fluornatropyrochlore, fluorcalciopyrochlore, fluorstrontiopyrochlore, fluorkenopyrochlore, oxynatropyrochlore, oxyplumbopyrochlore, oxyyttropyrochlore-(Y), kenoplumbopyrochlore, fluorcalciomicrolite, oxycalciomicrolite, kenoplumbomicrolite, hydromicrolite, hydrokenomicrolite, oxycalciobetafite, oxyuranobetafite, fluornatroroméite, fluorcalcioroméite, oxycalcioroméite, and oxyplumboroméite. For these, there are only chemical or crystalstructure data. Type specimens need to be defined. Potential candidates for several other species exist, but are not sufficiently well characterized to grant them any official status. Ancient chemical data refer to wet-chemical analyses and commonly represent a mixture of minerals. These data were not used here. All data used represent results of electron-microprobe analyses or were obtained by crystal-structure refinement. We also verified the scarcity of crystal-chemical data in the literature. There are crystalstructure determinations published for only nine pyrochlore-supergroup minerals:

Liandratite from Karkonosze pegmatites, Sudetes, Southwestern Poland

“…Liandratite shows a strong compositional similarity to the U-rich member of the pyrochlore group -uranopyrochlore (□,U 4+ ) 2 Nb 2 O 6 (O,OH,F) (Atencio et al 2010); however, it has a different U oxidation state. Unfortunately, to the author's knowledge, uranopyrochlore is still a rather theoretical member of the pyrochlore group because there is currently no species fulfilling the classification criteria proposed by Atencio et al (2010) for this mineral.…”

“…Unfortunately, to the author's knowledge, uranopyrochlore is still a rather theoretical member of the pyrochlore group because there is currently no species fulfilling the classification criteria proposed by Atencio et al (2010) for this mineral. Only one analysis in the literature satisfactorily meets the dominant valence rule regarding the U content in the A-site: analysis 9 from Chibiny (Chakhmouradian and Mitchell 2002).…”

Secondary tungsten minerals in quartz veins in the Ishidera area, Wazuka, Kyoto Prefecture, Japan: anthoinite, mpororoite, and Fe-free hydrokenoelsmoreite

“…According to the new nomenclature proposed by Atencio et al (2010), this elsmoreite reported by Williams et al (2005) is a specimen of the type hydrokenoelsmoreite. The hydrokenoelsmoreite discovered by Williams et al is nearly Al -free, whereas this hydrokenoelsmoreite from the Wazuka district contains a considerable amount of Al 2 O 3 .…”

“…Of these three, only ferritungstite has been found at several locations in Japan (e.g., Matsubara et al, 1994, andTsunoda andShimizu, 1995), while the other two have not been reported to be found anywhere in Japan. Recently, however, Atencio et al (2010) proposed a new nomenclature scheme for the pyrochlore supergroup to which these three minerals belong, and these minerals were classified under a new group "hydrokenoelsmoreite." Thus, the present mineral (sample B) should be called hydrokenoelsmoreite.…”

The association of oxygen-bearing minerals of chalcophile elements in the orogenetic zone related to the “mixed series” complex near Nežilovo, Republic of Macedonia

“…6, analysis 1 in Table 4) is not approved by the Commission on New Minerals Nomenclature and Classification of the International Mineralogical Assosiation. Moreover, this mineral is not listed among pyrochloresupergroup species for which analytical evidence is deemed adequate [25]. Consequently, hydroxyplumbobetafite is a potentially new mineral species that needs further investigations.…”