The new mineral markeyite (IMA2016-090), Ca9(UO2)4(CO3)13·28H2O, was found in the Markey mine, San Juan County, Utah, USA, where it occurs as a secondary phase on asphaltum in association with calcite, gypsum and natrozippeite. The mineral is pale yellowish-green with white streak and fluoresces bright bluish white under a 405 nm laser. Crystals are transparent and have vitreous to pearly lustre. It is brittle, with Mohs hardness 1½ to 2, irregular fracture and three cleavages: perfect on {001}; good on {100} and {010}. The measured density is 2.68 g cm–3. Crystals are blades, flattened on {001} and elongate on [010], exhibiting the forms {100}, {010}, {001}, {110}, {101}, {011} and {111}. Markeyite is optically biaxial (–) with α = 1.538(2), β = 1.542(2) and γ = 1.545(2) (white light); the measured 2V is 81(2)°; the dispersion is r < v (weak); the optical orientation is X = c, Y = b, Z = a; and pleochroism is X = light greenish yellow, Y and Z = light yellow (X > Y ≈ Z). Electron microprobe analyses (energy-dispersive spectroscopy mode) yielded CaO 18.60, UO3 42.90, CO2 21.30 (calc.) and H2O 18.78 (calc.), total 101.58 wt.% and the empirical formula Ca8.91(U1.01O2)4(CO3)13·28H2O. The six strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 10.12(69)(001), 6.41(91)(220,121), 5.43(100)(221), 5.07(33)(301,002,131), 4.104(37)(401,141) and 3.984(34)(222). Markeyite is orthorhombic, Pmmn, a = 17.9688(13), b = 18.4705(6), c = 10.1136(4) Å, V = 3356.6(3) Å3 and Z = 2. The structure of markeyite (R1 = 0.0435 for 3427 Fo > 4σF) contains uranyl tricarbonate clusters (UTC) that are linked by Ca–O polyhedra forming thick corrugated heteropolyhedral layers. Included within the layers is an additional disordered CO3 group linking the Ca–O polyhedra. The layers are linked to one another and to interlayer H2O groups only via hydrogen bonds. The structure bears some similarities to that of liebigite.

The new mineral fluorarrojadite-(BaNa), ideally BaNa4CaFe13Al(PO4)11(PO3OH)F2 was found on the dump of Elisabeth adit near Gemerská Poloma, Slovakia. It occurs in hydrothermal quartz veins intersecting highly fractionated, topaz–zinnwaldite S-type leucogranite. Fluorarrojadite-(BaNa) is associated with fluorapatite, ‘fluordickinsonite-(BaNa)’, triplite, viitaniemiite and minor amounts of other minerals. It forms fine-grained irregular aggregates up to 4 cm x 2 cm, which consist of individual anhedral grains up to 0.01 mm in size. It has a yellowish-brown to greenish-yellow colour, very pale yellow streak and a vitreous to greasy lustre. Mohs hardness is ~4½ to 5. The fracture is irregular and the tenacity is brittle. The measured density is 3.61(2) g cm–3 and calculated density is 3.650 g cm–3. Fluorarrojadite-(BaNa) is biaxial (+) and nonpleochroic. The calculated refractive index based on empirical formula is 1.674. The empirical formula (based on 47 O and 3 (OH + F) apfu) is A1(Ba0.65K0.35)Σ1.00 A2Na0.35 B1(Na0.54Fe0.46)Σ1.00 B2Na0.54Ca(Ca0.74Sr0.20Pb0.02Ba0.04)Σ1.00Na2 Na3Na0.46 M(Fe7.16Mn5.17Li0.37Mg0.12Sc0.08Zn0.06Ga0.02Ti0.02)Σ13.00 Al1.02P11O44PO3.46(OH)0.54 W(F1.54OH0.46). Fluorarrojadite-(BaNa) is monoclinic, space group Cc, a = 16.563(1) Å, b = 10.0476(6) Å, c = 24.669(1) Å, β = 105.452(4)°, V = 3957.5(4) Å3 and Z = 4. The seven strongest reflections in the powder X-ray diffraction pattern are [dobs in Å, (I), hkl]: 3.412, (21), 116; 3.224, (37), 206; 3.040, (100), 42$\bar 4$; 2.8499, (22), 33$\bar 3$; 2.7135, (56), 226; 2.5563, (33), 028 and 424; 2.5117, (23), 040. The new mineral is named according to the nomenclature scheme of arrojadite-group minerals, approved by the IMA CNMNC. In fluorarrojadite-(BaNa), Fe2+ is a dominant cation at the M site (so the root-name is arrojadite) and two suffixes are added to the root-name according to the dominant cation of the dominant valence state at the A1 (Ba2+) and B1 sites (Na+). A prefix fluor is added to the root-name as F– is dominant over (OH)– at the W site.

Melcherite (IMA2015-018), ideally Ba2Na2Mg[Nb6O19]·6H2O, occurs as a vug mineral in the carbonatite of the Jacupiranga mine, Cajati county, São Paulo state, Brazil, associated with dolomite, calcite, magnetite, pyrrhotite, tochilinite, ‘pyrochlore’ and fluorapatite. This is also the type locality for zirkelite, quintinite, menezesite and pauloabibite. The mineral forms irregular, tabular crystals up to 200 µm in maximum dimension. Melcherite is transparent and displays a vitreous lustre; it is beige with a white streak. It is non-fluorescent. The mineral displays perfect cleavage on {001}. Chemical composition varies from Ba2Na2Mg[Nb6O19].6H2O to (BaK)(NaCa)Mg[Nb6O19].6H2O. Empirical formulae for the first and the second compositions are: (Ba1.75K0.19)Σ1.94(Na1.80Ca0.19)Σ1.99(Mg0.96Mn0.02Al0.02)Σ1.00Nb6.02O19.00·6H2O and (Ba0.99K1.00)Σ1.99(Na1.02Ca0.96)Σ1.98(Mg0.95Mn0.05)Σ1.00Nb6.02O19.00·6H2O, respectively. Data for a single crystal with the second composition are: trigonal, R$\bar 3$, a = 9.0117(6) Å, c = 23.3986(16) Å, V = 1645.64(19) Å3 and Z = 3. Calculated density for this formula is 3.733 g/cm3, and the calculated mean refractive index is 1.924. Melcherite is a hexaniobate that has structural layers parallel to the xy plane that stack along the c axis with simultaneous 1/3 [110] displacement so as to produce an R lattice. The melcherite structure is built by layers of [(Ba,K)(O,H2O)9] polyhedra and the [Nb6O19]8− super-octahedron (Lindqvist anion) interconnected by [(Na,Ca)O6] polyhedra. Cations of Mg2+ are bonded to six water molecules each and are not associated with Lindqvist oxygen ions. The mineral is named in honour of Geraldo Conrado Melcher (1924–2011), a pioneer in Jacupiranga carbonatite studies.

A new mineral arsenowagnerite, Mg2(AsO4)F, the arsenate analogue of wagnerite, was found in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated closely with johillerite, tilasite, anhydrite, hematite, fluorophlogopite, cassiterite, calciojohillerite, aphthitalite and fluoborite. Arsenowagnerite occurs as equant to tabular crystals up to 1 mm across combined in interrupted crusts up to 0.1 cm × 1.5 cm × 3 cm. The mineral is transparent, light yellow, lemon-yellow, greenish-yellow or colourless and has a vitreous lustre. Arsenowagnerite is brittle, with Mohs hardness of ~5. Cleavage is distinct, the fracture is uneven. Dcalc = 3.70 g cm–3. Arsenowagnerite is optically biaxial (+), α = 1.614(2), β = 1.615(2), γ = 1.640(2) and 2Vmeas = 25(5)°. Wavenumbers of the strongest absorption bands in the IR spectrum (cm–1) are: 874, 861, 507, 491 and 470. The chemical composition (average of six electron-microprobe analyses, wt.%) is: MgO 38.72, CaO 0.23, MnO 0.32, CuO 0.60, ZnO 0.05, Fe2O3 0.11, TiO2 0.03, SiO2 0.08, P2O5 0.18, V2O5 0.03, As2O5 54.96, SO3 0.10, F 8.91 and –O=F –3.75, total 100.57. The empirical formula calculated on the basis of 5 (O + F) apfu is: (Mg1.98Cu0.02Mn0.01Ca0.01)Σ2.02(As0.99P0.01)Σ1.00O4.03F0.97. Arsenowagnerite is monoclinic, P21/c, a = 9.8638(3), b = 12.9830(3), c = 12.3284(3) Å, β = 109.291(3)°, V = 1490.15(7) Å3 and Z = 16. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 5.80(41)(002), 5.31(35)(120), 3.916(37)($\bar 2$21), 3.339(98)(221, 023), 3.155(65)(202), 3.043(100)($\bar 1$41), 2.940(72)($\bar 2$04), 2.879(34)($\bar 3$22) and 2.787(51)(320, $\bar 1$24). The crystal structure was solved from single-crystal X-ray diffraction data, R = 0.0485. Arsenowagnerite is isostructural to wagnerite-Ma2bc. The crystal structure is built by almost regular AsO4 tetrahedra, distorted MgO4F2 octahedra and distorted MgO4F trigonal bipyramids.

This study provides the first detailed mineralogical data on platinum-group element (PGE) mineralization of the Waterberg Project, in a previously unknown segment of the Bushveld Complex located in the Southern Marginal Zone of the Limpopo Belt. The lower ultramafic F zone is dominated by sperrylite (up to 82 area%) with minor Pt–Pd bismuthotellurides, Pd–Ni arsenides, Au–Ag alloy, Rh–Pt sulfoarsenides and rare Pt–Fe alloys. The upper more felsic-rich gabbroic T zone is dominated by Pt–Pd bismuthotellurides (up to 90 area%), Pd tellurides and Au–Ag alloy with rare sperrylite, braggite, Pd stannides and antimonides. The platinum-group minerals (PGM) of the F zone are associated mainly with magmatic base-metal sulfides (pyrrhotite, troilite, chalcopyrite and pentlandite), that have undergone alteration during significant serpentinization, accompanied by the formation of the secondary sulfide assemblage. The T zone in a leucogabbroic sequence contains relics of magmatic sulfides and is characterized by the development of the indicative chalcopyrite-millerite-pyrite assemblage, which is associated with widespread hydrothermal quartz and hydrous silicates (amphiboles, phlogopite, epidote and chlorite). The fluid-induced style of PGM remobilization, the high Au/PGE and the high proportion of native gold in the high-grade T zone ores in the magnetite-bearing leucogabbroic rocks are unique to the Bushveld Complex. The genesis of the T ores is interpreted as a result of primary PGE enrichment in the zone of interaction between the first influxes of the Upper Zone fertile melt and a resident gabbroic melt at the top of the Troctolite-Gabbronorite-Anorthosite (TGA) fractionated sequence with subsequent fluid remobilization. Whether the hydrothermal overprint facilitated the PGE sequestration in a favourable setting or dispersed the pre-existing magmatic concentrations along fluid pathways remains essentially unresolved at the current stage.

Two new minerals of the graftonite group, graftonite-(Mn), ideally M(1)MnM(2),M(3)Fe2(PO4)2, and graftonite-(Ca), ideally M(1)CaM(2),M(3)Fe2(PO4)2, were discovered in phosphate nodules of two beryl–columbite–phosphate pegmatites at Lutomia and Michałkowa, respectively, in the Góry Sowie Block, Lower Silesia, southwest Poland. Graftonite-(Mn) is pinkish brown, whereas graftonite-(Ca) shows more brownish colouration. Both minerals have a vitreous lustre, a good cleavage observed along (010) and irregular fracture; both are transparent and neither of them is fluorescent. They are brittle and have a Mohs hardness of ~5. The minerals are non-pleochroic, colourless in all orientations, biaxial (+), with mean refractive indices α = 1.710(2) and 1.690(2), β = 1.713(2) and 1.692(2), and γ = 1.725(2) and 1.710(5), respectively. With complete order of Ca at the M(1) site, the formulae of the holotype crystals are M(1)(Mn0.70Ca0.30)M(2),M(3)(Fe1.34Mn0.60Mg0.06Zn0.01)Σ3(PO4)2 for graftonite-(Mn) and M(1)(Ca0.98Mn0.02)M(2),M(3)(Fe1.38Mn0.56Mg0.05)Σ3(PO4)2 for graftonite-(Ca). Both crystal chemistry and crystal-structure refinement (R1 = 2.34 and 1.63%, respectively) indicate that the M(1) site is occupied dominantly by Mn in graftonite-(Mn) and by Ca in graftonite-(Ca), and the M(2) and M(3) sites are occupied by Fe2+ and Mn2+, with Fe2+ dominant over Mn2+ at the aggregate M(2) + M(3) sites. Graftonite-(Mn) and graftonite-(Ca) are isostructural with graftonite, M(1)FeM(2),M(3)Fe2(PO4)2 (monoclinic system; space-group symmetry P21/c), with the unit-cell parameters a = 8.811(2) Å, b = 11.494(2) Å, c = 6.138(1) Å, β = 99.23(3)° and V = 613.5(4) Å3, and a = 8.792(2) Å, b = 11.743(2) Å, c = 6.169(1) Å, β = 99.35(3)° and V = 628.5(1) Å3, respectively. The densities calculated on the basis of molar weights and unit-cell volumes are 3.793 g/cm3 for graftonite-(Mn) and 3.592 g/cm3 for graftonite-(Ca). The eight strongest lines in powder X-ray diffraction patterns on the basis of single-crystal data are, respectively [d, Å, I (hkl)]: 2.874, 100, (230 + 040); 2.858, 79, (221); 3.506, 73, (130); 2.717, 79, ($\bar{3}$11); 2.952, 55, (131); 2.916, 53, ($\bar{1}$12); 2.899, 44, (300); 3.016, 35, ($\bar{1}$02); and 3.654, 100, (130); 2.979, 85, (221); 3.014, 77, (230); 3.042, 76, (040 + $\bar{1}$12); 2.834, 68, ($\bar{3}$11); 3.097, 57, (131); 3.133, 56, ($\bar{1}$02); 2.542, 30, (311). Both minerals are common primary phosphates in phosphate nodules, occurring as lamellar intergrowths with sarcopside ± triphylite/lithiophilite, products of exsolution from a (Li,Ca)-rich graftonite-like parent phase crystallized at high temperature from P-bearing hydrosaline melts.

The crystal structures of carlfrancisite, ideally Mn32+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]8(OH)42, hexagonal (rhombohedral), R3̄m with Z = 6, and unit-cell parameters: a = 8.2238(2), c = 205.113(6) Å and V = 12013.5(4) Å3, from the Kombat mine, Otavi Valley, Namibia, and mcgovernite, ideally Zn3(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]8(OH)42, hexagonal (rhombohedral), R3̄m with Z = 6, and unit-cell parameters: a = 8.2061(3), c = 204.118(8) Å and V = 11903.8(6) Å3, from Sterling Hill, New Jersey, have been solved by direct methods and refined to R1 values of 3.37 and 5.02% for 3837 and 3772 unique observed reflections, respectively; they are isostructural. Chemical analysis by electron microprobe and crystal-structure refinement gave the following compositions: carlfrancisite: As2O5 12.89, As2O3 3.33, P2O5 0.50, V2O5 0.74, SiO2 8.96, Al2O3 0.78, FeO 0.22, MnO 53.25, MgO 9.37, H2O(calc) 8.42, sum 98.50 wt.%; mcgovernite: As2O5 13.06, As2O3 3.71, SiO2 9.34, Al2O3 0.20, FeO 1.38, MnO 44.58, ZnO 8.81, MgO 8.89, H2O(calc) 8.24, sum 98.21 wt.%. The H2O contents and the valence states of As were determined by crystal-structure analysis.

There are 18 crystallographically distinct cation sites in both carlfrancisite and mcgovernite. There are two [4]-coordinated As sites fully occupied by As5+, and four T sites occupied by Si and As5+ in solid solution. The As(3) site has triangular pyramidal coordination with <As(3)–O> distances of 1.808 and 1.817 Å, typical of As3+. The Z(1) site, occupied by Mn2+ in carlfrancisite and Zn in mcgovernite, has tetrahedral coordination, and the Z(2) site is only partly occupied by Mg and Mn2+ in both structures. There are nine M sites, all of which are octahedrally coordinated and contain dominantly Mn2+ and Mg, with minor Al and Fe. There are three cation sites with significant vacancies: As(3), Z(2), M(3), and there are complicated patterns of short-range order involving the cations and vacancies at these sites.

The carlfrancisite–mcgovernite structure contains 84 layers of approximately close-packed polyhedra along one translation on c. The anions in the structure are arranged in approximately close-packed layers orthogonal to the c axis. Fourteen layers stack along the c axis in the sequence |**hhchch•hchchh| (* denotes a layer of anions displaced from close packed). There are eight distinct layers of cation-centred polyhedra that repeat via a centre of symmetry at the origin, and via the R-centering to give 84 layers per unit-cell.

Two quintinite polytypes, 3R and 2T, which are new for the Kovdor alkaline-ultrabasic complex, have been structurally characterized. The crystal structure of quintinite-2T was solved by direct methods and refined to R1 = 0.048 on the basis of 330 unique reflections. The structure is trigonal, P$\bar 3$c1, a = 5.2720(6), c = 15.113(3) Å and V = 363.76(8) Å3. The crystal structure consists of [Mg2Al(OH)6]+ brucite-type layers with an ordered distribution of Mg2+ and Al3+ cations according to the $\sqrt 3 $ × $\sqrt 3 $ superstructure with the layers stacked according to a hexagonal type. The complete layer stacking sequence can be described as …=Ab1C = Cb1A=…. The crystal structure of quintinite-3R was solved by direct methods and refined to R1 = 0.022 on the basis of 140 unique reflections. It is trigonal, R$\bar 3$m, a = 3.063(1), c = 22.674(9) Å and V = 184.2(1) Å3. The crystal structure is based upon double hydroxide layers [M2+,3+(OH)2] with disordered distribution of Mg, Al and Fe and with the layers stacked according to a rhombohedral type. The stacking sequence of layers can be expressed as …=АB = BC = CA=… The study of morphologically different quintinite generations grown on one another detected the following natural sequence of polytype formation: 2H → 2T → 1M that can be attributed to a decrease of temperature during crystallization. According to the information-based approach to structural complexity, this sequence corresponds to the increasing structural information per atom (IG): 1.522 → 1.706 → 2.440 bits, respectively. As the IG value contributes negatively to the configurational entropy of crystalline solids, the evolution of polytypic modifications during crystallization corresponds to the decreasing configurational entropy. This is in agreement with the general principle that decreasing temperature corresponds to the appearance of more complex structures.

A new member of the gadolinite supergroup, gadolinite-(Nd), IMA2016-013, ideally Nd2FeBe2Si2O10, was found in the Malmkärra mine, ~3.5 km WSW of Norberg, south-central Sweden, where it occurs in association with fluorbritholite-(Ce), västmanlandite-(Ce), dollaseite-(Ce), bastnäsite-(Ce) and tremolite. Gadolinite-(Nd) forms anhedral grains up to 150 µm in size, commonly occurring as aggregates of olive green colour. The crystals are transparent with vitreous to adamantine lustre. Gadolinite-(Nd) is brittle with conchoidal fracture, no cleavage or parting was observed. It has a white streak, the Mohs hardness is 6.5–7 and the calculated density is 4.86 g cm–3. Optically, the mineral is weakly pleochroic in shades of olive green, biaxial (–), nα = 1.78(1), nβ(calc.) = 1.80, nγ = 1.81(1) measured in white light, 2V(meas.) = 62(3)°. Electron-microprobe and laser ablation inductively coupled plasma mass spectrometry analysis [in wt.%] provided SiO2 21.77, Y2O3 5.49, La2O3 2.78, Ce2 O3 14.04, Pr2O3 3.28, Nd2O3 19.27, Sm2O3 5.30, Eu2O3 0.24, Gd2O3 4.10, Tb2O3 0.36, Dy2O3 1.32, Ho2O3 0.18, Er2O3 0.38, MgO 0.51, CaO 0.14, MnO 0.10, FeO 10.62, B2O3 0.10, BeOcalc. 8.99, H2Ocalc. 0.55 and total 99.52 giving the following empirical formula (based on 2 Si): (Nd0.632 Ce0.472Y0.268Sm0.168Gd0.125Pr0.110La0.094Dy0.039Ca0.014Er0.011Tb0.011Eu0.008Ho0.008)∑1.957(Fe0.816Mg0.070Mn0.008)∑0.894(Be1.984B0.016)∑2.000Si2O9.660OH0.337. A weak Raman vibration band at ~3525 cm–1 confirms the presence of water in the structure. Gadolinite-(Nd) is monoclinic, P21/c, with a = 4.8216(3) Å, b = 7.6985(4) Å, c = 10.1362(6) Å, β = 90.234(4)°, V = 376.24(6) Å3 and Z = 2. The strongest X-ray diffraction lines are [dobs in Å (hkl) Irel]: 4.830 (100) 72, 3.603 (021) 37, 3.191(-112) 52, 3.097 (013) 35, 2.888 (121) 100, 2.607(113) 49, 2.412 (200) 24. Along with the Malmkärra mine, gadolinite-(Nd) was also recorded also at Johannagruvan and Nya Bastnäs. The minerals of the gadolinite subgroup together with fluorbritholite-(Ce) incorporate the highest fraction of medium-to-heavy rare-earth elements among associated rare-earth element minerals in the Malmkärra mine and possibly in all Bastnäs-type deposits.

Inclusions of platinum-group minerals (PGM) within alluvial isoferroplatinum nuggets from the Freetown Peninsula, Sierra Leone, are aligned with their shape determined by the structure of their host. The edges of the majority of the inclusions lie at 0°, 45° or 90° to external crystal edges of the nugget which shows that the inclusions are not randomly oriented earlier minerals incorporated within their host. The inclusions are later infills, probably formed at the surface of the nugget during growth and subsequently enclosed by the growing nugget. PGM on the present surface of the nugget represent the last stage of this partnership. A single nugget containing abundant inclusions is described here but similar features are observed in other nuggets from the same area. The inclusions contain laurite (RuS2), irarsite–hollingworthite (IrAsS–RhAsS), Pd–Te–Bi–Sb phases, Ir-alloy, Os-alloy, Pd-bearing Au, an Rh–Te phase, Pd–Au alloy and Pd–Pt–Cu alloy. PGM found on the nugget surface include laurite, irarsite and cuprorhodsite (CuRh2S4). The Pd–Te–Bi–Sb phases may include Sb-rich keithconnite (Pd20S7) and compositions close to the kotulskite–sobolevskite solid-solution series (PdTe–BiTe). Textural evidence suggests that formation of the nuggets began with the isoferroplatinum host and the voids were filled starting intergrowths of laurite and irarsite–hollingworthite with both laurite and irarsite–hollingworthite often showing compositional zonation and each of them replacing the other. Filling of the voids probably continued with Pd-Cu-bearing gold, Sb-rich keithconnite (Pd,Pt)20.06(Te,Sb,Bi)6.94, keithconnite, telluropalladinite Pd9(Te,Bi)4, RhTe and finally Ir-alloy and then Os-alloy. The nuggets are thought to be neoform growths in the organic- and bacterial-rich soils of the tropical rain forest cover of the Freetown intrusion. The mineralogical assemblage in the layered gabbros of the intrusion has been previously shown to differ from the alluvial assemblage in the rivers and these inclusions, not seen in Pt3Fe in the unaltered rocks, add a further item to the catalogue of differences.

Silicate minerals enriched in V, Cr and Mn including garnets and epidote-supergroup members, in association with amphiboles, albite, hyalophane, titanite, chamosite, sulfides and other minerals occur in Devonian black shales near Čierna Lehota in the Strážovské vrchy Mountains, Slovakia. The garnets have high concentrations of V, Cr and Mn (up to 17 wt.% V2O3, ≤11 wt.% Cr2O3 and ≤ 21 wt.% MnO) and several compositional types. Vanadian-chromian grossular (Grs 1) usually preserves primary metamorphic oscillatory zoning, whereas solid solutions between goldmanite (Gld 2A,B), V- and Cr-rich grossular and spessartine (Grs 2A,B, Sps 2) form irregular domains or crystals with variable zoning. Dominant substitutions in the garnets include CaMn–1 and (V,Cr)Al–1, resulting in coupled Ca(V,Cr)Mn–1Al–1. Epidote-supergroup minerals occur as abundant anhedral crystals with variable compositional zoning. Nearly all crystals have a complete zoning sequence beginning with REE-rich allanite-(La), followed by mukhinite and by V- and Cr-rich clinozoisite to mukhinite and V- and Cr-poor clinozoisite. In common with garnets, the epidote-supergroup minerals are enriched in V, Cr and Mn (<7 wt.% V2O3, <5 wt.% Cr2O3 and <3 wt.% MnO). Lanthanum is the dominant REE (up to 11.5 wt.% La2O3) in allanite-(La). The composition of epidote-supergroup minerals is controlled by REEFe2+(CaAl)–1, REEMg(CaAl)–1, REEMn2+(CaAl)–1 and REEFe2+(CaFe3+)–1 substitutions introducing REE, together with VAl–1 and CrAl–1 substitutions. The negative Ce and slightly positive Eu anomalies displayed in chondrite-normalized patterns and enrichment in V, Cr and Mn are ascribed to the geochemical properties of the protolith. The minerals investigated exhibit multi-stage evolution: (1) presumed low-grade greenschist-facies metamorphism; and (2) development of V- and Cr-rich zones in both garnet- and epidote-supergroup minerals which result from late-Variscan contact metamorphism due to granitic intrusion of the Suchý Massif. Decreased temperature following the metamorphic peak probably resulted in the formation of REE-, V- and Cr-poor clinozoisite and secondary garnet.

The carbonate-dominated Mesozoic sequence of the Transdanubian Mountain Range contains Triassic, uranium-enriched phosphorite layers and Cretaceous, REE-enriched nodular phosphorite. Detailed investigation of these deposits may have an economic benefit because of their large U and REE contents. The dominant minerals in the Triassic phosphorite are carbonate-bearing fluorapatite (CFA) and calcite. According to the electron-probe microanalysis (EPMA) the U is mainly associated with the CFA crystals. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurement shows that CFA contains 137–612 ppm U and 113–261 ppm total REE + Y. The LA-ICP-MS U-Pb age of the uppermost phosphorite horizon is 237 ± 11 Ma, which conforms with the stratigraphic age of the host limestone.

The Cretaceous nodular phosphorite occurs on the base of an Aptian crinoid-bearing limestone mostly in the form of encrustations around bio- and silicic-clasts, but the clasts also contain phosphorite. The main minerals in these crusts are CFA, calcite, quartz, glauconite and Fe-oxide-hydroxides. Based on EPMA the REE enrichment is related to CFA and LA-ICP-MS measurements show that it contains 748–2953 ppm total REE + Y.

The redox-sensitive proxies and the shape of NASC normalized REE patterns indicate that both phosphorites formed in anoxic environments. There are significant differences between these deposits such as appearance, rock-forming minerals, and U and REE contents which indicate differences in their sedimentary environments. The present results suggest that the Triassic phosphorite was formed by inorganic precipitation in a reducing environment close to sea-mounts. The Cretaceous occurrence resulted from a concentric growth mechanism in cold, ascending seawater at the continental margin environment during the anoxic Selli Event (OAE 1a) and/or Paquier Episode (OAE 1b). The critical raw material contents were derived from other sources.

The hydrated carbonate mineral ikaite (CaCO3·6H2O) is thermodynamically unstable at all known conditions on Earth. Regardless, ikaite has been found in marine sediments, as tufa columns and in sea ice. The reason for these occurrences remains unknown. However, cold temperatures (<6°C), high pH and the presence of Mg2+ and SO42– in these settings have been suggested as factors that promote ikaite formation. Here we show that Mg concentration and pH are primary controls of ikaite precipitation at 5°C. In our experiments a sodium carbonate solution was mixed with seawater at a temperature of 5°C and at a constant rate. To test the effect of Mg2+ and SO42– we used synthetic seawater which allowed us to remove these elements from the seawater. The pH was controlled by different ratios of Na2CO3 and NaHCO3 in the carbonate solution. We found that ikaite precipitated when both seawater and synthetic seawater from which SO4 had been removed were used in the experiments. However, ikaite did not precipitate in experiments conducted with synthetic seawater from which Mg had been removed. In these experiments, calcite precipitated instead of ikaite. By varying the Mg concentration of the synthetic seawater and the pH of the sodium carbonate solution, we constructed a kinetic stability diagram for ikaite and calcite as a function of Mg concentration and pH. One possible explanation of our finding is that Mg2+ inhibits calcite nucleation and thereby allows metastable ikaite to form instead.

A new mineral species, fluorlamprophyllite (IMA2013-102), ideally Na3(SrNa)Ti3(Si2O7)2O2F2, has been found in the Poços de Caldas alkaline massif, Morro do Serrote, Minas Gerais, Brazil. Alternatively, the idealized chemical formula could be written as (SrNa)[(Na3Ti)F2][Ti2(Si2O7)2O2], setting the large interlayer cations before the cations of the layer. Fluorlamprophyllite is the F-analogue of lamprophyllite. It is associated with aegirine, analcime, natrolite, nepheline and microcline. Fluorlamprophyllite crystals are brownish-orange and bladed. The mineral is transparent with a pale yellow streak and an adamantine lustre. It is brittle and has a Mohs hardness of ~3; cleavage is perfect on {100} and no parting was observed. The calculated density is 3.484 g/cm3. Optically, fluorlamprophyllite is biaxial (+), with α = 1.735(7), β = 1.749(7) and γ = 1.775(9) and 2Vmeas = 72(3)°. An electron microprobe analysis produced an average composition (wt.%) (9 points) of Na2O 10.63(30), K2O 0.47(3), SiO2 30.51(13), SrO 18.30(24), MgO 0.81(17), Al2O3 0.23(2), CaO 1.11(7), MnO 5.03(38), TiO2 27.41(87), Fe2O3 2.45(37), F 2.86(23), plus H2O 1.00 (added to bring the total close to 100%), –O = F –1.20, with the total = 98.61%. The elements Nb and Ba were sought, but contents were below microprobe detection limits. The resultant chemical formula was calculated on the basis of 18 (O + F) atoms per formula unit. The addition of 1.00 wt.% H2O brought [F+(OH)] = 2 pfu, yielding (Na2.63Sr1.35Mn0.54Ca0.15Mg0.15K0.08)Σ4.90(Ti2.63Fe0.24Al0.04)Σ2.91Si3.89O16[F1.15(OH)0.85]Σ2.00. The mineral is monoclinic, with space group C2/m and unit-cell parameters a = 19.255(2), b = 7.0715(7), c = 5.3807(6) Å, β = 96.794(2)° and V = 727.5(1) Å3. The structure is a layered silicate inasmuch as the O atoms are arranged in well-defined, though not necessarily close-packed layers.

A natural olivenite single crystal was submitted to in situ high-temperature single-crystal X-ray diffraction from room temperature (RT) to 500°C. Unit-cell parameters were measured at regular intervals of 25°C, and complete datasets collected at T = 25, 50, 100, 150, 200, 250, 300, 400 and 500°C. Evolution of unit-cell parameters and structure refinements indicates that olivenite undergoes a structural phase transition from P21/n to Pnnm at ~200°C, and eventually becomes isostructural with the other members of the olivenite-mineral group. Volume expansion with temperature is larger in the monoclinic phase – where it follows a non-linear trend – than in the orthorhombic one. Axial and volume expansion coefficients of the orthorhombic olivenite phase are positive and linear and similar to those of the other Cu-bearing member of the mineral family, namely libethenite, but rather different from those of the Zn-analogue arsenate adamite.

Distortion of Cu polyhedra is quite high in the olivenite monoclinic phase at RT and goes towards a relative regularization with increasing T until the phase transition occurs. In the orthorhombic phase, no significant variation of the polyhedral distortion parameters is observed with increasing temperature, and maximum expansion is along the b direction and governed by corner-sharing. Landau potential provides a good representation of the macroscopic changes associated with the phase transition, coupling between the strains and the order parameter is responsible for the nearly tricritical character of the transition.

Beusite-(Ca), ideally Ca${\rm Mn}_{\rm 2}^{2 +} $(PO4)2, is a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada. It occurs in a beryl–columbite–phosphate rare-element pegmatite where it is commonly intergrown with triphylite–lithiophilite or sarcopside, and may form by exsolution from a high-temperature (Li,Ca)-rich graftonite-like parent phase. It occurs as pale-brown lamellae 0.1–1.5 mm wide in triphylite, and is pale brown with a vitreous lustre and a very pale-brown streak. It is brittle, has a Mohs hardness of 5, and the calculated density is 3.610 g/cm3. Beusite-(Ca) is colourless in plane-polarized light, and is biaxial (+) with α = 1.685(2), β = 1.688(2), γ = 1.700(5), and the optic axial angle is 46.0(5)°. It is non-pleochroic with X || b; Y ˄ a = 40.3° in β obtuse; Z ˄ a = 49.7° in β acute. Beusite-(Ca) is monoclinic, has space group P21/c, a = 8.799(2), b = 11.724(2), c = 6.170(1) Å, β = 99.23(3)°, V = 628.3(1) Å3 and Z = 4. Chemical analysis by electron microprobe gave P2O5 41.63, FeO 19.43, MnO 23.63, CaO 15.45, sum 100.14 wt.%. The empirical formula was normalized on the basis of 8 anions pfu: (Ca0.94Fe0.92Mn1.13)Σ2.99(PO4)2.00. The crystal structure was refined to an R1 index of 1.55%. Beusite-(Ca) is a member of the graftonite group with Ca completely ordered at the [8]-coordinated M(1) site.

Nanoscale characterization (TEM on FIB-SEM-prepared foils) was undertaken on feldspars undergoing transformation from early post-magmatic (deuteric) to hydrothermal stages in granites hosting the Olympic Dam Cu-U-Au-Ag deposit, and from the Cu-Au skarn at Hillside within the same iron-oxide copper-gold (IOCG) province, South Australia. These include complex perthitic textures, anomalously Ba-, Fe-, or REE-rich compositions, and REE-flourocarbonate + molybdenite assemblages which pseudomorph pre-existing feldspars. Epitaxial orientations between cryptoperthite (magmatic), patch perthite (dueteric) and replacive albite (hydrothermal) within vein perthite support interface-mediated reactions between pre-existing alkali-feldspars and pervading fluid, irrespective of micro-scale crystal morphology. Such observations are consistent with a coupled dissolution-reprecipitation reaction mechanism, which assists in grain-scale element remobilization via the generation of transient interconnected microporosity. Micro-scale aggregates of hydrothermal hyalophane (Ba-rich K-feldspar), crystallizing within previously albitized areas of andesine, reveal a complex assemblage of calc-silicate, As-bearing fluorapatite and Fe oxides along reaction boundaries in the enclosing albite-sericite assemblage typical of deuteric alteration. Such inclusions are good REE repositories and their presence supports REE remobilization at the grain-scale during early hydrothermal alteration. Iron-metasomatism is recognized by nanoscale maghemite inclusions within ‘red-stained’ orthoclase, as well as by hematite in REE-fluorocarbonates, which reflect broader-scale zonation patterns typical for IOCG systems. Potassium-feldspar from the contact between alkali-granite and skarn at Hillside is characterized by 100–1000 ppm REE, attributable to pervasive nanoscale inclusions of calc-silicates, concentrated along microfractures, or pore-attached. Feldspar replacement by REE-fluorcarbonates at Olympic Dam and nanoscale calc-silicate inclusions in feldspar at Hillside are both strong evidence for the role of feldspars in concentrating REE during intense metasomatism. Differences in mineralogical expression are due to the availability of associated elements. Lattice-scale intergrowths of assemblages indicative of Fe-metasomatism, REE-enrichment and sulfide deposition at Olympic Dam are evidence for a spatial and temporal relationship between these processes.

The Conakry Igneous Complex is a mafic-ultramafic intrusion emplaced contemporaneously with the opening of the Atlantic, forming a complex, 55 km x 5 km dyke-like body within which three main episodes of injection have been recognized, characterized by a lack of mineral layering. Unit 1 consists of dunite and related facies, Unit 2 of wehrlite and pyroxene peridotite and Unit 3 corresponds to various gabbro facies. Units 1 and 2 constitute the Kaloum Peninsula; Unit 3 is its NW extension, forming the 1010 m high Mount Kakoulima. Unit 3 intrudes the two previous units and corresponds to a tholeiitic liquid that crystallized in an almost closed system, and thus exhibits a strong differentiation trend, in contrast to Units 1 and 2. Mineral compositions suggest the existence of a deeper magma chamber where a first stage of differentiation occurred.

Disseminated base-metal sulfides (BMS) are present in all units of the complex and earlier descriptions have mentioned a “massive sulfide layer” with 2 to 4 g/t PGE. Platinum-group minerals (PGM) are almost everywhere included in or attached to composite Ni–Fe–Cu sulfides. Most PGM grains form complex associations resulting either from exsolution or alteration. It is characteristic of the Conakry Igneous Complex PGM, described here for the first time, to be dominated by (Pd,Pt)(Te,Bi) minerals with rare Pd,Sn and Pd,Pb compositions and an absence of Pt,Pd sulfides and Pt,Pd antimonides.

The constant association of the PGM with the BMS shows that the magmatic sulfide liquid acts as an efficient collector of PGE. In such a dynamic environment, the process leading to the formation of massive sulfides must be sought in the accumulation of sulfides in the conduit following host-rock assimilation. Accordingly, considering the multiple injection processes that characterize the whole intrusion, the potential for discovering additional Ni–Cu–PGE mineralization in the Conakry Igneous Complex remains high.

Parisite-(La) (IMA2016-031), ideally CaLa2(CO3)3F2, occurs in a hydrothermal vein crosscutting a metarhyolite of the Rio dos Remédios Group, at the Mula mine, Tapera village, Novo Horizonte county, Bahia, Brazil, associated with hematite, rutile, almeidaite, fluocerite-(Ce), brockite, monazite-(La), rhabdophane-(La) and bastnäsite-(La). Parisite-(La) occurs as residual nuclei (up to 5 mm) in steep doubly-terminated pseudo-hexagonal pyramidal crystals (up to 8.2 cm). Parisite-(La) is transparent, yellow-green to white, with a white streak and displays a vitreous (when yellow-green) to dull (when white) lustre. Cleavage is distinct on pseudo-{001}; fracture is laminated, conchoidal, or uneven. The Mohs hardness is 4 to 5, and it is brittle. Calculated density is 4.273 g cm−3. Parisite-(La) is pseudo-uniaxial (+), ω = 1.670(2) and ε = 1.782(5) (589 nm). The empirical formula normalized on the basis of 11 (O + F) atoms per formula unit (apfu) is Ca0.98(La0.83Nd0.51Ce0.37Pr0.16Sm0.04Y0.03)Σ1.94C3.03O8.91F2.09. The IR spectrum confirms the absence of OH groups. Single-crystal X-ray studies gave the following results: monoclinic (pseudo-trigonal), space group: C2, Cm, or C2/m, a = 12.356(1) Å, b = 7.1368(7) Å, c = 28.299(3) Å, β = 98.342(4)°, V = 2469.1(4) Å3 and Z = 12. Parisite-(La) is the La-dominant analogue of parisite-(Ce).

Tombarthite-(Y) is discredited as a mineral species. No type material was available, but material used for the original description has been located and neotype material defined. The main reason for the erroneous description of tombarthite-(Y) is the result of chemical analyses being carried out on heated material, which removed elements such as C and F. New semi-quantitative chemical analyses show that at least F is present in the fresh material, but absent after a heating scheme identical to that of the original description. Modern powder X-ray diffraction methods (XRD) confirm that the material identified as tombarthite-(Y) is a mixture of metamict and crystalline phases. Consequently, what was known as tombarthite-(Y) is not a mixture of the same minerals in equal amounts in different samples, but mixtures of various minerals depending on the sample. The main minerals identified are thalénite-(Y), xenotime-(Y) and kainosite-(Y). The discreditation of tombarthite-(Y) relies on new analyses of a large number of samples from the collection of the Natural History Museum (NHM) in Oslo and has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (proposal 16-K).