Marco Pasero

Nomenclature of the apatite supergroup minerals

The apatite supergroup includes minerals with a generic chemical formula IX M12 VII M23( IV TO4)3 X( Z ¼ 2); chemically they can be phosphates, arsenates, vanadates, silicates, and sulphates. The maximum space group symmetry is P63/m, but several members of the supergroup have a lower symmetry due to cation ordering and deviations from the ideal topology, which may result in an increase of the number of the independent sites. The apatite supergroup can be formally divided into five groups, based on crystal-chemical arguments: apatite group, hedyphane group, belovite group, britholite group, and ellestadite group. The abundance of distinct ions which may be hosted at the key-sites (M ¼ Ca 2þ , Pb 2þ , Ba 2þ , Sr 2þ , Mn 2þ , Na þ , Ce 3þ , La 3þ ,Y 3þ , Bi 3þ ;T ¼ P 5þ , As 5þ ,V 5þ , Si 4þ ,S 6þ ,B 3þ ;X ¼ F � , (OH) � , Cl � ) result in a large number of compositions which may have the status of distinct mineral species. Naming of apatite supergroup minerals in the past has resulted in nomenclature inconsistencies and problems. Therefore, an ad hoc IMA-CNMNC Subcommittee was established with the aim of rationalizing the nomenclature within the apatite supergroup and making some order among existing and potentially new mineral species. In addition to general recommendations for the handling of chemical (EPMA) data and for the allocation of ions within the various sites, the main recommendations of this subcommittee are the following: 1. Nomenclature changes to existing minerals. The use of adjectival prefixes for anions is to be preferred instead of modified Levinson suffixes; accordingly, six minerals should be renamed as follows: apatite-(CaF) to fluorapatite, apatite-(CaOH) to hydroxylapatite, apatite-(CaCl) to chlorapatite, ellestadite-(F) to fluorellestadite, ellestadite-(OH) to hydroxylellestadite, phospho- hedyphane-(F) to fluorphosphohedyphane. For the apatite group species these changes return the names that have been used in thousands of scientific paper, treatises and museum catalogues over the last 150 years. The new mineral IMA 2008-009, approved without a name, is here named stronadelphite. Apatite-(SrOH) is renamed fluorstrophite. Deloneite-(Ce) is renamed deloneite. The new mineral IMA 2009-005 is approved with the name fluorbritholite-(Y).

A Milk and Ochre Paint Mixture Used 49,000 Years Ago at Sibudu, South Africa

Gas chromatography/mass spectrometry, proteomic and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) analyses of residue on a stone flake from a 49,000 year-old layer of Sibudu (South Africa) indicate a mixture of ochre and casein from milk, likely obtained by killing a lactating wild bovid. Ochre powder production and use are documented in Middle Stone Age South African sites but until now there has been no evidence of the use of milk as a binder. Our analyses show that this ochre-based mixture was neither a hafting adhesive nor a residue left after treating animal skins, but a liquid mixture consisting of a powdered pigment mixed with milk; in other words, a paint medium that could have been applied to a surface or to human skin. The significance of our finds also lies in the fact that it establishes the antiquity of the use of milk as a binder well before the introduction of domestic cattle in South Africa in the first millennium AD.

Recommended nomenclature for the sapphirine and surinamite groups (sapphirine supergroup)

Abstract Minerals isostructural with sapphirine-1A, sapphirine-2M, and surinamite are closely related chain silicates that pose nomenclature problems because of the large number of sites and potential constituents, including several (Be, B, As, Sb) that are rare or absent in other chain silicates. Our recommended nomenclature for the sapphirine group (formerly aenigmatite group) makes extensive use of precedent, but applies the rules to all known natural compositions, with flexibility to allow for yet undiscovered compositions such as those reported in synthetic materials. These minerals are part of a polysomatic series composed of pyroxene or pyroxene-like and spinel modules, and thus we recommend that the sapphirine supergroup should encompass the polysomatic series. The first level in the classification is based on polysome, i.e. each group within the supergroup corresponds to a single polysome. At the second level, the sapphirine group is divided into subgroups according to the occupancy of the two largest M sites, namely, sapphirine (Mg), aenigmatite (Na), and rhönite (Ca). Classification at the third level is based on the occupancy of the smallest M site with most shared edges, M7, at which the dominant cation is most often Ti (aenigmatite, rhönite, makarochkinite), Fe3+ (wilkinsonite, dorrite, høgtuvaite) or Al (sapphirine, khmaralite); much less common is Cr (krinovite) and Sb (welshite). At the fourth level, the two most polymerized T sites are considered together, e.g. ordering of Be at these sites distinguishes høgtuvaite, makarochkinite and khmaralite. Classification at the fifth level is based on XMg = Mg/(Mg + Fe2+) at the M sites (excluding the twolargest and M7). In principle, this criterion could be expanded to include other divalent cations at these sites, e.g. Mn. To date, most minerals have been found to be either Mg-dominant (XMg > 0.5), or Fe2+-dominant (XMg < 0.5), at these M sites. However, XMg ranges from 1.00 to 0.03 in material described as rhönite, i.e. there are two species present, one Mg-dominant, the other Fe2+-dominant. Three other potentially new species are a Mg-dominant analogue of wilkinsonite, rhönite in the Allende meteorite, which is distinguished from rhönite and dorrite in that Mg rather than Ti or Fe3+ is dominant at M7, and an Al-dominant analogue of sapphirine, in which Al > Si at the two most polymerized T sites vs. Al < Si in sapphirine. Further splitting of the supergroup based on occupancies other than those specified above is not recommended.

Crystal structure refinement of sahlinite, Pb14(AsO4)2O9Cl4

Abstract The crystal structure of sahlinite [Pb14(AsO4)2O9Cl4] from Långban (Sweden) has been refined up to R = 0.071 using single-crystal diffraction data collected at the Elettra synchrotron facility. Sahlinite is monoclinic, space group C2/c, with a = 12.704(4), b = 22.576(5), c = 11.287(4) Å , β = 118.37(3)º. Sahlinite is isostructural with kombatite, its vanadium counterpart. Both are derivatives of the litharge form of PbO. In the structure of sahlinite there are seven independent Pb atoms, which are linked to Cl and/or O atoms, with coordination number ranging from V to VIII. The coordination polyhedra are irregularly shaped, due to the 6s2 lone-pair effect displayed by Pb2+.

The systematics of the spinel-type minerals: An overview

Abstract Compounds with a spinel-type structure include mineral species with the general formula AB2φ4, where φ can be O2-, S2-, or Se2-. Space group symmetry is Fd3̄m, even if lower symmetries are reported owing to the off-center displacement of metal ions. In oxide spinels (φ = O2-), A and B cations can be divalent and trivalent (“2-3 spinels”) or, more rarely, tetravalent and divalent (“4-2 spinels”). From a chemical point of view, oxide spinels belong to the chemical classes of oxides, germanates, and silicates. Up to now, 24 mineral species have been approved: ahrensite, brunogeierite, chromite, cochromite, coulsonite, cuprospinel, filipstadite, franklinite, gahnite, galaxite, hercynite, jacobsite, magnesiochromite, magnesiocoulsonite, magnesioferrite, magnetite, manganochromite, qandilite, ringwoodite, spinel, trevorite, ülvospinel, vuorelainenite, and zincochromite. Sulfospinels (φ = S2-) and selenospinels (φ = Se2-) are isostructural with oxide spinels. Twenty-one different mineral species have been approved so far; of them, three are selenospinels (bornhardtite, trüstedtite, and tyrrellite), whereas 18 are sulfospinels: cadmoindite, carrollite, cuproiridsite, cuprokalininite, cuprorhodsite, daubréelite, ferrorhodsite, fletcherite, florensovite, greigite, indite, kalininite, linnaeite, malanite, polydymite, siegenite, violarite, and xingzhongite. The known mineral species with spinel-type structure are briefly reviewed, indicating for each of them the type locality, the origin of the name, and a few more miscellaneous data. This review aims at giving the state-of-the-art about the currently valid mineral species, considering the outstanding importance that these compounds cover in a wide range of scientific disciplines.

New minerals and nomenclature modifications approved in 2012 and 2013

The information given here is provided by the IMA Commission on New Minerals, Nomenclature and Classification for comparative purposes and as a service to mineralogists working on new species. Each mineral is described in the following format: Mineral name, if the authors agree on its release prior to the full description appearing in press Chemical formula Type locality Full authorship of proposal E-mail address of corresponding author Relationship to other minerals Crystal system, Space group; Structure determined, yes or no Unit-cell parameters Strongest lines in the X-ray powder diffraction pattern Type specimen repository and specimen number Citation details for the mineral prior to publication of full description Citation details concern the fact that this information will be published in the Mineralogical Magazine on a routine basis, as well as being added month by month to the Commissions web site. It is still a requirement for the authors to publish a full description of the new mineral. NO OTHER INFORMATION WILL BE RELEASED BY THE COMMISSION IMA No. 2012-039 Ca1–2Fe[(Si,Al,Be)5Be2O13(OH)2]·2H2O In a syenite pegmatite at Langangen, Blafjell, Norway (59°5′34″N 9°41′38″E) and the A/S Granite Quarry, Tvedalen, Vestfold, Norway J. Grice*, R. Kristiansen, H. Friis, R. Rowe, R.S. Selbekk, M. Cooper, A.O. Larsen and G. Poirier *E-mail: jgrice@mus-nature.ca Interrupted framework zeolite Monoclinic: P 21/ c ; structure determined a = 8.759(5), b = 4.864(2), c = 31.258(7) A, β = 90.31(3)° 15.555(100), 4.104(29), 3.938(36), 3.909(60), 3.820(30), 3.251(66), 3.186(27), 2.884(64) Type material is deposited in the collections of the Canadian Museum of Nature, Ottawa, Canada, specimen number CNMMC 86554, and the Natural History Museum, Oslo, Norway, specimen numbers 43434 and 43435 How to cite: Grice, J., Kristiansen, R., Friis, H., Rowe, R., Selbekk, R.S., Cooper, M., Larsen, A.O. and …

Dessauite, (Sr,Pb) (Y,U) (Ti,Fe (super 3+) ) 20 O 38 , a new mineral of the crichtonite group from Buca della Vena Mine, Tuscany, Italy

Abstract Dessauite, a new mineral in the crichtonite group, occurs within cavities in calcite veins as tabular {001} rhombohedral, black, millimeter-sized crystals at Buca della Vena Mine, Apuan Alps (Tuscany, Italy). It is associated with derbylite, hematite, rutile, karelianite, siderite, and calcite. Dessauite is trigonal, space group R3̅, with a = 9.197(1) Å, α = 68.75(2)°. Optically, dessauite is opaque and shows low bireflectance and very weak pleochroism. Electron microprobe analyses led to the following simplified chemical formula: (Sr,Pb)(Y,U)(Ti,Fe3+)20O38. The crystal structure of dessauite was refined from single-crystal X-ray diffraction data to R = 0.065. Dessauite is isostructural with the others members of the crichtonite group; a peculiar structural feature is the presence of additional, partially occupied octahedral sites. A comparison of the crystal-chemical formulas of all the minerals within the crichtonite group is presented. In view of the structural information, the analytical data have been re-arranged on the basis of the crystal-chemical formula ABC18T2O38, rather than AM21O38.

Pumpellyite-(Al), a new mineral from Bertrix, Belgian Ardennes

Pumpellyite-(Al), ideally Ca 2 (Al,Fe 2+ ,Mg)Al 2 (SiO 4 )(Si 2 O 7 )(OH,O) 2 ·H 2 O, is a newly approved mineral species from Bertrix, Ardennes mountains, Belgium. It occurs as radiating fibrous aggregates reaching 5 mm in diameter, constituted by acicular crystals associated with calcite, K-feldspar and chlorite. Pumpellyite-(Al) is transparent to translucent and exhibits an emerald-green to white colour, sometimes with bluish tinges. The lustre is vitreous and the streak is colourless. The mineral is non-fluorescent, brittle, and shows a perfect {100} cleavage. The estimated Mohs hardness is 5½, and the calculated density is 3.24 g/cm 3 . Pumpellyite-(Al) is biaxial positive, α = 1.678(2), β = 1.680(2), γ = 1.691(1) (λ = 590 nm), colourless in thin section, 2 V = 46°, Y = b , no dispersion. Electron-microprobe analyses gave SiO 2 37.52, Al 2 O 3 25.63, MgO 1.99, FeO 4.97, MnO 0.11, CaO 23.21, BaO 0.01, Na 2 O 0.03, K 2 O 0.02, H 2 O calc . 6.71, total 100.20 wt. %. The resulting empirical formula, calculated on the basis of 8 cations, is (Ca 1.99 Na 0.01 ) ∑2.00 (Al 0.42 Fe 2+ 0.33 Mg 0.24 Mn 0.01 ) ∑1.00 Al 2.00 (SiO 4 )(Si 2 O 7 )(OH) 2.42 0.58H 2 O. The simplified formula is Ca 2 AlAl 2 (SiO 4 )(Si 2 O 7 )(OH) 3 , which requires SiO 2 38.16, Al 2 O 3 32.38, CaO 23.74, H 2 O 5.72, Total 100.00 wt. %. The unit-cell parameters, refined from X-ray powder diffraction data, are: a = 8.818(2), b = 5.898(2), c = 19.126(6) A, β = 97.26(3)°, V = 986.7(4) A 3 , space group A 2/ m. The eight strongest lines in the powder pattern [ d- values(in A)( I )( hkl )] are: 4.371(65)(200), 3.787(80)(202), 3.040(70)(204), 2.912(95)(300), 2.895(100)(302), 2.731(40)(206), 2.630(35)(311), 2.191(45)(402). Pumpellyite-(Al) belongs to the pumpellyite group, and corresponds to the Al-rich compositions where the M1 and M2 sites contain Al as predominant cation. The crystal structure of pumpellyite-(Al) has been refined by the Rietveld method, based on an X-ray powder diffraction pattern, to R Bragg = 7.09 %. The infrared spectrum is similar to those of minerals of the pumpellyite group. The mineral species and name were approved by the Commission on New Minerals and Mineral Names, IMA (no. 2005-016).

Fluorcalciobritholite, Ca,REE)5[(Si,P)O4]3F, a new mineral: description and crystal chemistry

The new mineral fluorcalciobritholite, ideally Ca 3 Ce 2 (SiO 4 ) 2 (PO 4 )F, has been found at Mount Kukisvumchorr, Khibiny alkaline complex, Kola Peninsula, Russia, in veinlets which contains aggregates of orthoclase, nepheline, sodalite and biotite in association with grains of fayalite, gadolinite-(Ce), zircon, monazite-(Ce), zirconolite (“polymignite”), fluorapatite, fluorite, molybdenite, lollingite and graphite. Fluorcalciobritholite forms long-prismatic hexagonal crystals up to 0.5 x 10 mm; the main crystal form is the hexagonal prism {10–10}. The mineral is transparent, with a pale pinkish to brown colour and a white streak. The hardness (Mohs) is 5.5, and the observed density is 4.2(1) g/cm 3 . Optically, it is uniaxial (−) with ω 1.735(5), e 1.730(5). Electron microprobe gave the following empirical formula based on [Si+P+S] = 3 apfu : [Ca 2.80 (Ce 0.93 La 0.54 Nd 0.26 Y 0.18 Pr 0.08 Sm 0.03 Gd 0.03 Dy 0.02 Yb 0.02 Er 0.01 ) ∑2.12 Th 0.04 Mn 0.03 Sr 0.02 ] ∑4.99 [(Si 1.94 P 1.06 ) ∑3 O 12 ] [F 0.76 O 0.22 Cl 0.01 ] ∑0.99 (Z = 2). The IR spectrum of metamict fluorcalciobritholite from Siberia showed a marked similarity with those of hydroxylbritholite-(Ce) and hydroxylbritholite-(Y). The strongest lines of the X-ray powder pattern [ d in A ( I ) ( hkl )] are: 3.51 (45) 002, 3.15 (70) 102, 2.85 (100) 211, 121, 2.78 (60) 300. The mineral is hexagonal, space group P 6 3 / m , with a = 9.580(7), c = 6.985(4) A, V = 555.2(7) A 3 . The crystal structure was refined from single-crystal X-ray diffraction data to R F = 0.029. Fluorcalciobritholite, whose simplified formula is (Ca,REE) 5 [(Si,P)O 4 ] 3 F, differs from fluorbritholite in having Ca > ∑REE, and differs from fluorapatite in having Si > P. Its compositional field falls within the limits Ca 2.5 REE 2.5 (SiO 4 ) 2.5 (PO 4 ) 0.5 F (boundary with fluorbritholite) and Ca 3.5 REE 1.5 (SiO 4 ) 1.5 (PO 4 ) 1.5 F (boundary with fluorapatite). Both the mineral and its name have been approved by the IMA Commission on New Minerals and Mineral Names.

X-ray and HRTEM study of sursassite: Crystal structure, stacking disorder, and sursassite-pumpellyite intergrowth

Sursassite is monoclinic, space group P21/m, a=8.70, b=5.79, c=9.78 Å, β=108.9°. The crystal structure was determined with X-rays and refined to R=0.065, obtaining Mn2Al3[(OH)3(SiO4)(Si2O7)] as ideal crystal chemical formula. Sursassite, isostructural with macfallite Ca2Mn3[(OH)3(SiO4)(Si2O7)], is closely related to pumpellyite Ca2Al3[(OH)3(SiO4)(Si2O7)]. In fact both sursassite and pumpellyite, apart from the different chemical composition, are built up by common structural layers, which are repeated by different stacking vectors. As a result, faulted stacking sequences are energetically possible.Examination by high resolution transmission electron microscopy (HRTEM) shows that frequent (001) pumpellyite-like lamellae are intergrown with thicker (001) sursassite lamellae. Usually, the guest lamellae are a few unit cells thick along [001] and continuous along the (001) plane, although also rare interrupted lamellae are found.