Commission On New Minerals , Nomenclature And Classification Research Articles

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC)

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC)

WinPclclas, a Windows Program for Pyrochlore Supergroup Minerals

Abstract A Microsoft® Visual Basic program, WinPclclas, has been developed to calculate the chemical formulae of pyrochlore supergroup minerals (PSM) based on data obtained from wet-chemical and electron-microprobe analyses. These are also classified following the nomenclature scheme adopted by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association for PSM (IMA-10) and including both subsequent group and species updates. The program considers classification among the 33 IMA-approved PSM, as well as ten species that have not been approved, adhering to the general formula A2B2X6Y and considering the dominant ions at the A, B, and Y sites. It considers PSM represented by the pyrochlore, microlite, roméite, elsmoreite, and betafite groups, along with unassigned members of the ralstonite and coulsellite groups. Mineral formulae of the PSM are calculated based on the ideal number of B cations being two apfu, owing to the potential for vacancies at the A, X, and Y sites. WinPclclas operates in four stages: (1) it estimates cation and anion contents provided by input chemical data; (2) it determines the dominant cation and anion at the A, B, and Y sites; (3) it assigns the PSM to one of the seven groups, based on the dominant cation at the B site (i.e., W6+, Nb5+, Ta5+, Sb5+, Ti4+, Al3+, and Mg2+); and (4) it classifies the pyrochlore species into an appropriate group, based on the dominant cation at the A site and the dominant anion at the Y site. The H2O (wt.%) content for the PSM is estimated by stoichiometric constraints. WinPclclas allows users to: (1) enter up to 51 input variables for mineral-chemical analyses; (2) type and load multiple PSM compositions in the data entry section; (3) edit and load the Microsoft® Excel files used in calculating, classifying, and naming the PSM, together with the total monovalent to hexavalent cation, and (4) store all the calculated parameters in the output of a Microsoft® Excel file for further data evaluations. The program is distributed as a self-extracting setup file, including the necessary support files used by the program, a help file, and representative sample data files.

Newsletter 76

Newsletter 76

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 75

Andrieslombaardite, RhSbS, a new platinum-group mineral from the platiniferous Onverwacht Pipe, Republic of South Africa

Abstract A hundred years after the discovery of the Merensky Reef in 1924, it is appropriate to present the new mineral andrieslombaardite in honour of Andries Frederik Lombaard who was instrumental in its discovery. Andrieslombaardite, RhSbS, was first described as an unknown mineral from placer deposits associated with the Tulameen Alaskan-Uralian type complex, British Colombia, Canada (Raicevic and Cabri, 1976) but has since been reported from several other deposits including the platiniferous Driekop, Mooihoek, and Onverwacht pipes in the eastern Bushveld Complex, South Africa. The mineral and the name were approved by the Commission on New Minerals Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA no. 2022-076) based on data in the co-type samples from Onverwacht and a co-type sample from the Yubdo stream, Birbir River, Ethiopia. Andrieslombaardite in the Onverwacht sample is a single 8 x 20 μm grain attached to laurite in a matrix of altered silicate and Fe-oxyhydroxide minerals. In the Yubdo samples, there are many grains of pale brownish gray andrieslombaardite up to 25 x 55 μm in size, included in Pt-Fe alloys, some associated with erlichmanite, and others attached to bornite and chalcopyrite. The reflectance values (R%) measured in air and in oil at the COM wavelengths are 48.3 and 33.0 (470 nm), 49.3 and 34.0 (546 nm), 51.0 and 35.9 (589 nm), and 51.8 and 36.7 (650 nm). The colour values x, y, Y, λd, and Pe in air are 0.317, 0.322, 50.3, 580, and 3.2, and in oil are 0.319, 0.324, 35.6, 579, and 4.5. The composition of andrieslombaardite is ideally RhSbS, but it contains variable amounts of Fe, Pt, Pd, and Ir that may substitute for Rh. The mineral is cubic with unit-cell dimensions of a = 6.0278(4) Å, V = 219.01(6) Å3 and Z = 4. It was synthesised at 400 and 550°C using stoichiometric elemental amounts. It is a member of the cobaltite group. The mineralisation of the intrusive dunite pipes was probably introduced at high temperatures, under magmatic conditions. The primary assemblages were to a certain degree overprinted and redistributed by low-temperature hydrothermal fluids. The Pt-Fe alloys from Yubdo containing PGM inclusions such as andrieslombaardite in the Yubdo-Alaskan-type complex were formed at some post-magmatic stage owing to PGE remobilisation during hydrothermal or metamorphic episodes.

On the definition of distinct mineral species: A critique of current IMA–CNMNC procedures

AbstractThe criteria for the definition of a new mineral species currently used by the Commission on New Minerals Nomenclature and Classification (CNMNC) of the International Mineralogical Association are critically examined. In particular, the rule of the dominant constituent can violate the laws of conservation of electric charge. A series of additional rules: (1) valency-imposed double site-occupancy; (2) the dominant-valency rule; and (3) the site-total-charge approach, have been developed in an attempt to correct this error. However, none of these rules can overcome the fundamental flaw introduced by the rule of the dominant constituent, and the chemical formulae resulting from application of these rules can violate the requirements of an end-member, particularly that of electroneutrality. As a result, the IMA–CNMNC rules cannot derive end-member formulae for some groups of minerals, giving rise to many ad hoc decisions in defining distinct mineral species.

Arrojadite-group nomenclature: sigismundite reinstated

Abstract. The name sigismundite has been reinstated from arrojadite-(BaFe) following the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) recommendations defined by Hatert et al. (2013) for the preservation of historical names. The name change was approved by the CNMNC, voting proposal 22-C. The new mineral symbol for sigismundite is Sigi. Sigismundite honours Pietro Sigismund (1874–1962), and this paper outlines his significant contributions to Italian mineralogy.

IMA–CNMNC approved mineral symbols

Abstract Several text symbol lists for common rock-forming minerals have been published over the last 40 years, but no internationally agreed standard has yet been established. This contribution presents the first International Mineralogical Association (IMA) Commission on New Minerals, Nomenclature and Classification (CNMNC) approved collection of 5744 mineral name abbreviations by combining four methods of nomenclature based on the Kretz symbol approach. The collection incorporates 991 previously defined abbreviations for mineral groups and species and presents a further 4753 new symbols that cover all currently listed IMA minerals. Adopting IMA–CNMNC approved symbols is considered a necessary step in standardising abbreviations by employing a system compatible with that used for symbolising the chemical elements.

New data on nordite-(Ce) and the establishment of the nordite supergroup

AbstractA nomenclature scheme has been set up for the nordite supergroup of minerals, which have the general formula A2BXYZT6O17 and where A = Na; B = Na, Ca; X = Sr, Ca, Ba; Y = REE, Sr; Z = Zn, Fe, Mn, Mg and T = Si. The nordite supergroup includes nordite-(La), nordite-(Ce), ferronordite-(La), ferronordite-(Ce) and manganonordite-(Ce), as well as meieranite which is considered as an unassigned member of the nordite supergroup. In the known nordite-group minerals the Y site is occupied by rare earth elements (REE), while in meieranite the Y site is occupied by Sr. The dominant element on the tetrahedral Z site determines the prefix used in the mineral name. New rootnames must be given to species with a different dominant element on the A, B or X sites. Nordite supergroup minerals are orthorhombic, although nordite-group minerals and meieranite crystallise in the Pcca and P21nb space groups, respectively. The proposed nomenclature scheme for the nordite supergroup has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA). In addition, new chemical and structural investigations were performed on nordite-(Ce) from Illutalik (Igdlutalik), South Greenland, leading to the first crystal structure refinement for nordite-(Ce).

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IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 51

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IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 50

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IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 49

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IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 48

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IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 47

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 45

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 45

Discreditation of bobdownsite and the establishment of criteria for the identification of minerals with essential monofluorophosphate (PO3F2–)

Bobdownsite, IMA number 2008-037, was approved as a new mineral by the Commission on New Minerals, Nomenclature and Classification (CNMNC) as the fluorine endmember of the mineral whitlockite. The type locality of bobdownsite is in Big Fish River, Yukon Canada, and bobdownsite was reported to be the first naturally occurring mineral with essential monofluorophosphate (PO3F2-). The type specimen of bobdownsite has been reinvestigated by electron probe microanalysis (EPMA), and our data indicate that fluorine abundances are below detection in the mineral. In addition, we conducted detailed analysis of bobdownsite from the type locality by gas chromatography isotope ratio mass spectrometry, Raman spectroscopy, EPMA, and NMR spectroscopy. These data were compared with previously published data on synthetic monofluorophosphate salts. Collectively, these data indicate that bobdownsite is indistinguishable from whitlockite with a composition along the whitlockite-merrillite solid solution. Bobdownsite is therefore discredited as a valid mineral species. An additional mineral, krasnoite, has been purported to have monofluorophosphate components in its structure, but reexamination of those data indicate that F- in krasnoite forms bonds with Al, similar to OH- bonded to Al in perhamite. Consequently, krasnoite also lacks monofluorophosphate groups, and there are currently no valid mineral species with monofluorophosphate in their structure. We recommend that any future reports of new minerals that contain essential monofluorophosphate anions be vetted by abundance measurements of fluorine, vibrational spectroscopy (both Raman and FTIR), and where paramagnetic components are permissibly low, NMR spectroscopy. Furthermore, we emphasize the importance of using synthetic compounds containing monofluorophosphate anions as a point of comparison in the identification of minerals with essential monofluorophosphate. Structural data that yield satisfactory P-F bond lengths determined by X-ray crystallography, coupled with direct chemical analyses of fluorine in a material do not constitute sufficient evidence alone to identify a new mineral with essential monofluorophosphate anions.

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 46

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 46

Introduction to the special issue of Meteoritics & Planetary Science on “Shock metamorphism and high pressure phases in meteorites and terrestrial impactites”

Interplanetary collisions of planetary bodies represent a fundamental process that affected all planets and moons of the solar system since its formation. They occur on an extremely wide scale of projectile and target sizes, and with a large range of impact velocities. Hypervelocity collisions result in the propagation of shock waves in the colliding bodies and as a consequence in “shock metamorphism” of the impacted regions. Shock metamorphism of solid rocks and sediments has been identified on all terrestrial planets and moons from which samples are available so far, i.e., Earth, Moon, Mars, and asteroids. Shock waves with an intensity exceeding the Hugoniot elastic limit lead to distinct changes in the constituent minerals of rocks ranging from mechanical deformation to phase transitions such as isotropization and formation of high-pressure phases, and to melting. With increasing pressure, whole rock melting and finally vaporization occurs. This special issue is devoted to the observation and interpretation of these effects on the basis of the current state of research. It covers both natural shock metamorphism and shock wave experiments as well as numerical modeling of shock metamorphism and shock wave physics in general. The last decade has seen important changes in this field: novel techniques in submicrometer-scale structural and chemical analysis, marked improvements in established techniques such as FIB-TEM and EPMA and synchrotron radiation analyses, and an increasing supply of meteorite material have largely increased the number of identified high-pressure minerals that form upon shock metamorphism. In fact, over the past 10 years more such minerals were discovered than in the previous four decades. Novel, ultrafast probes of structural and chemical states during shock experiments promise to reveal some of the fundamental mechanisms that occur during the initial states of shock compression. Efforts in three-dimensional modeling of dynamic stress evolution in polycrystalline aggregates suggest far more complex stress–temperature distribution patterns than conventional hydrocode simulations. This special issue is based on a workshop entitled “Shock metamorphism and high pressure phases in meteorites and terrestrial impactites” which was held on August 6 and 7, 2016, in conjunction with the 79th Annual Meeting of the Meteoritical Society in Berlin, Germany. The conveners were O. Tschauner, T. G. Sharp, and D. Stöffler. Since the date of acceptance of some of the contributions to this Special Issue, further articles about the topic of the Special Issue have been published. In addition, several new high-pressure phases in meteorites and in the Ries impact crater have been accepted by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA). The relevant references are the following: Bindi L. and Xie X. 2017. Shenzhuangite, IMA 2017-018. CNMNC Newsletter No. 38. Mineralogical Magazine 81:1033–1038. Ma C. and Tschauner O. 2017. Zagamiite, IMA 2015-022a. CNMNC Newsletter No. 36. Mineralogical Magazine 81:403–409. Ma C. and Tschauner O. 2017. Chenmingite, IMA 2017-036. CNMNC Newsletter No. 38. Mineralogical Magazine 81:1033–1038. Ma C., Tschauner O., Beckett J. R., Rossman G. R., Prescher C., Prakapenka V. B., Bechtel H. A., and MacDowell A. 2017. Liebermannite, KAlSi3O8, a new shock-metamorphic, high-pressure mineral from the Zagami Martian meteorite. Meteoritics & Planetary Science https://doi.org/10.1111/maps.13000. Tomioka N. and Miyahara M. 2017. High-pressure minerals in shocked meteorites. Meteoritics & Planetary Science 52:2017–2039. Tschauner O., Ma C., Lanzirotti A., and Newville M. 2017. Riesite, a new high pressure polymorph of TiO2 that forms upon shock-release comparison to (Zr,Ti)O2 in pseudotachylites, Goldschmidt Conference 2017, Abstract. Tschauner O. and Ma C. 2017. Stöfflerite, IMA 2017-062. CNMNC Newsletter No. 39. Mineralogical Magazine 81:1279–1286.

Epidote supergroup nomenclature: The names hancockite, niigataite and tweddillite reinstated

AbstractThe epidote-group nomenclature report by Armbruster et al. (2006) provides a clear and concise definition of the epidote group, and a set of consistent rules and naming conventions for establishing new subgroups and mineral species within what is now the epidote supergroup (Mills et al., 2009). In order to comply with these rules, it was decided to rename the already approved minerals hancockite, niigataite and tweddillite to epidote-(Pb), clinozoisite-(Sr) and manganipiemontite-(Sr), respectively. These names were already well established within the mineral community, and the renaming caused some controversy. Recent International Mineralogical Association guidelines (Hatert et al. 2013) have given priority to the historical provenance of names over nomenclature consistency. Hatert et al. (2013) state as a main principle that "retroactivity will not be applied", but that "Every change in nomenclature has to go through the CNMNC, and is examined on its own merit", thus establishing a mechanism for re-instating historical names on a case by case basis. The CNMNC (Commission on New Minerals, Nomenclature and Classification Committee of the International Mineralogical Association) has therefore decided, as an exception to the main principle, to re-instate hancockite, niigataite and tweddillite. In part to maintain the historical names but, more importantly, re-establish the link between the mineral names and their structural and chemical definitions.

New Compositional and Structural Data Validate the Status of Jamborite

Jamborite was originally described with the formula (Ni,Ni,Fe)(OH)(OH,S,HO) from Ca' de' Ladri and Monteacuto Ragazza near Bologna, and Castelluccio di Moscheda near Modena, Italy. Re-examination of the mineral from the type localities and Rio Vesale, Sestola, Val Panaro (Emilia-Romagna, Italy), led to the discovery of a crystal suitable for study by single-crystal and powder X-ray diffraction, SEM-EDS, and Raman spectroscopy. Jamborite crystallizes in the space group R3m, with the unit-cell parameters a 3.068(4) A, c 23.298(11) A, and Z = 3. The structure refinement (R = 0.0818) showed that jamborite contains brucite-like sheets of edge-sharing octahedra (Ni,M)(O,OH) with a distinctive double layer of partially occupied HO molecules between them. Raman data indicate that the sulfur is present as sulfate rather than sulfide. The new analytical data were recalculated on the basis of 1 (Ni+Ca+Co+Fe) to give the formula [(NiCa)(CoFe)]Σ (OH)Cl(HO)(SO)·0.900HO. The sulfur occupancy was too low to be located in the refinement, but the '1:1 ratio of M:S from the chemical analysis implies that SO replaces OH in the brucite sheet rather than sitting in the interlayer space. The splitting of the HO layer allows avoidance of short SO⋯HO distances. Thus, jamborite is not a member of the hydrotalcite supergroup. Jamborite is redefined as MM(OH)(SO)·nHO, where M is dominantly Ni, M is dominantly Co, x ≤ 1/3 and probably ≤ 1/7 (x =0.10 for the neotype sample), and n < (1-x). The low M/M ratio relative to honessite and hydrohonessite and high Co content may explain the rarity of jamborite as an early alteration product of millerite. The redefinition of jamborite and designation of the neotype specimen from Rio Vesale have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC), voting proposal 14-E.