The occurrence of pumpellyite in Late Cretaceous volcanic rocks of the Coloured Series, NE of Neyriz, is reported for the first time. The form of the pumpellyite and its chemistry are described. The mineral assemblages of the prehnite-pumpellyite facies of metamorphism are present, indicating that burial metamorphism has occurred, a new factor to be considered in the tectonic evolution of the Zagros suture zone.

Amphiboles of the tremolite-ferro-actinolite series from the Bergslagen district in central Sweden have between 0 and 46% of their M1-M3 sites occupied by Mn. These amphiboles are divided into two groups; (1) a group characterised by Mn (M1-M3) > (Mg or Fe) (M1-M3), and (2) a group with much lower contents of Mn (M1-M3), showing the following chemical characteristics: (a) Mn (M1-M3) never exceeds Fe (M1-M3); (b) in Mg-rich members of the group [Mg (M1-M3) > (Mn or Fe) (M1- M3)], the highest amounts of Mn (M1-M3) occur in amphiboles with about 2.20 Mg (M1-M3) per formula unit (pfu); in Fe-rich members of the group Fe [(M1-M3) > (Mg or Mn) (M1-M3)] high amounts of Mn (M1-M3) [> 0.4 Mn (MI-M3)] pfu only occur in amphiboles with >3.40 Fe (M1-M3) pfu; (d) the lowest amounts of Mn (M1-M3) occur in amphiboles with Mg (M1-M3) = Fe (M1-M3).

Mn (M4) increases with increasing amounts of Mn (M1-M3), indicating that solid solution towards the tirodite-dannemorite series is enhanced by incorporation of Mn (M1-M3).

Stalagmites and stalactites, as observed within natural caves, may develop inside geological repositories during constructional and post-operational periods. It is therefore important to understand actinide sorption within such materials. Towards this, experimental studies were carried out with 233U, 238Np (VI), 238Np (IV), 239Pu and 241Am radiotracers using natural speleothem samples collected from the Dharamjali cave of the Kumaon Lesser Himalayas, India. Petrological/mineralogical studies showed that natural speleothems have three general domains: (1) columnar calcite; (2) microcrystalline calcite; and (3) botryoidal aragonite – each with ferruginous materials. Results showed that all domains of speleothems can take up >99% actinides, irrespective of valence state and pH (1–6 range) of the solution. However, distribution coefficients were found to be at a maximum in aragonite for most of the actinides. Such data are very important for long-term performance and safety assessments of the deep geological repositories planned for the disposal of high-level nuclear wastes.

Stanleyite, a cobalt-blue mineral, occurs as efflorescent outgrowths on patronite from Cerro de Pasco, Minasragra, Peru. The determined composition is very close to the ideal formula VOSO4.6H2O and yields an empirical formula of V1.01O1.01S0.99O3.99 5.78H2O on the basis of O = 5 in the anhydrous part. X-ray powder data (31 lines) indexed on an orthorhombic cell give a 12.12, b 9.71, and c 14.92Å, cell volume 1755.8Å3 and Z = 8. Refractive indices are α 1.505, β 1.519, and γ 1.533, D is 1.95 (measured) and 2.01 (calculated), H = 1−1½ (Mohs). Thermal analysis and X-ray powder data show stanleyite to be quite different from minasragrite (the pentahydrate) which it clearly mimics. Associated minerals are potassium alum, pyrite, and quartz.

Mesaite (IMA2015-069), ideally (V2O7)3·12H2O, is a new mineral from the Packrat mine, Gateway district, Mesa County, Colorado, USA. Crystals of mesaite occur as orangish red blades up to 0.1 mm long and ∼10 μm thick. The streak is light pinkish orange and the lustre is vitreous, transparent. Mesaite has a brittle tenacity, {010} perfect cleavage; fracture is irregular, and no parting was observed. The mineral has a Mohs hardness ≈ 2. The measured density of mesaite is 2.74(1) g cm–3. Mesaite is biaxial (–), α = 1.760(calc), β = 1.780(5), γ = 1.795(5) in white light; the measured 2V value = 81(2)°. Dispersion is strong, r < v, and pleochroism is present in shades of brownish orange. Mesaite is monoclinic, P2/n, with a = 9.146(2), b = 10.424(3), c = 15.532(4) Å, β = 102.653(7)° and V = 1444.7(6) Å3. The strongest four diffraction lines in the powder diffraction pattern are [(dobs in Å, (Iobs), (hkl)]: 10.47 (100) (010), 2.881 (25) (132, 3̄12, 033, 310), 3.568 (24) (1̄14, 1̄23, 2̄13), 3.067 (17) (1̄24, 1̄32, 2̄23). The composition of mesaite was determined by electron microprobe, and yielded an empirical formula of Mn5.32Ca0.56Zn0.31V5.96As0.04O33H23.61 on the basis of 33 O atoms per formula unit (apfu).

The atomic arrangement of mesaite was solved and refined to R1 = 0.0600. The structure is formed of zigzag octahedral chains of edge-sharing Mn2+O6 octahedra. Oxygen atoms of the octahedra are shared with V2O7 groups, which link with adjacent octahedral chains to form {010} heteropolyhedral layers. The interlayer region contains Ca atoms and H2O groups. Each Ca bonds to two O6 atoms in the heteropolyhedral layer and to two fully occupied and six partially occupied O (H2O) sites in the interlayer, resulting in an effective Ca coordination of approximately seven. Similar zigzag chains of edge-sharing MnO6 octahedra decorated with V2O7 groups are also found in the mineral fianelite. Mesaite has beenapproved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2015-069). The name mesaite is conferred for Mesa County, Colorado, USA.

Ilvaite is sparsely disseminated in a serpentinized plagioclase wehrlite of the Asama igneous complex that underwent the Sambagawa regional metamorphism of pumpellyite-actinolite to greenschist facies. Ilvaite in the Asama complex is monoclinic (a = 13.019(5), b = 8.808(2), c = 5.850(4) Å, β = 90.19(4)°), and its composition is similar to the ideal end-member composition (). Ilvaite occurs in mats of serpentine (chrysotile); it probably formed during serpentinization, which might have accompanied the Sambagawa metamorphism. The associated secondary minerals include salitic clinopyroxene, magnetite and andradite. The ilvaite-free mineral assemblage that formed during the serpentinization is usually serpentine-clinopyroxene-magnetite, which is widespread in the complex. The phase relations between coexisting minerals suggest that the conditions during the formation of the ilvaite-bearing assemblage were reducing when compared to those of the assemblage serpentine-clinopyroxene-magnetite. The reducing conditions during the ilvaite formation were presumably brought about by hydrogen gas that1 was generated during the serpentinization of olivine.

Unusual irregular galena crystals and whiskers were found in close proximity in some druse cavities from the Gradishtc hydrothcrmal lead-zinc deposit in the Madan ore district, Bulgaria. The following crystal forms were observed: (1) straight thin [110] whiskers and thicker needles; (2) kinked whiskers; (3) curvilinear whiskers; (4) complex tortuous whiskers composed of segments with varying directions—[110], [100], [211], (5) thicker irregular elongated crystals. Combinations of these forms occur also. The detailed SEM study shows that all these formations are single crystals of extreme anisometricity, bounded by octahedral and cubic faces as well as by stepped surfaces of these forms. Surface structures such as longitudinal grooves, jagged edges, striations, pits, etc., are abundant.

It is assumed that these highly non-equilibrium crystals with large surface areas were formed through rapid directed growth from highly supersaturated solutions under a diffusional regime. Such special environments arose in the ore veins as a result of tectonic shocks leading locally to a drastic volume increase and P and T decrease in the solutions.

Crimsonite (IMA2014-095), PbFe3+2(PO 4)2(OH)2, the phosphate analogue of carminite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with fluorwavellite, goethite, hematite, hentschelite, plumbogummite and variscite on quartz. Crimsonite occurs in subparallel aggregates of deep red blades or plates flattened on {100} and up to 0.1 mm in maximum dimension. The streak is light purplish orange. Crystals are transparent and have adamantine lustre. The Mohs hardness is ∼3½, the tenacity is brittle, the fracture is irregular to splintery and an imperfect cleavage is likely on {101}. The calculated density is 5.180 g/cm3. Crimsonite is optically biaxial (+), with 2V = 85.5(5)° and γ – α = 0.011. Using the Gladstone-Dale relationship, the calculated indices of refraction are α = 2.021, β = 2.026 and γ = 2.032. The optical orientation is X = b; Y = a; Z = c and the pleochroism is X light orange, Y light yellow, Z red brown; Y < X < Z. Electron microprobe analyses provided PbO 40.69, CaO 0.60, ZnO 0.72, CuO 0.13, Fe2O3 23.36, Al2O3 0.34, V2O5 0.70, As2O5 12.05, P2O5 16.03, SO3 0.33 and H2O 3.64 (structure), total 98.59 wt.%. The empirical formula (based on 10 O apfu) is (Pb1.06Ca0.06)∑1.12(Fe1.71Zn0.05Al0.04Cu0.01)∑1.81(P1.32As0.61V0.05S0.02)∑2.00O8[(OH)1.64(H2O)0.36]∑2.00. Crimsonite is orthorhombic, Cccm, a = 16.2535(13), b = 7.4724(4), c = 12.1533(9) Å, V = 1476.04(17) Å3 and Z = 8. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å(I)(hkl)]: 5.86(42)(111); 4.53(45)(112); 3.485(64)(113); 3.190(100) (022); 3.026(40)(004); 2.902(54)(511); 2.502(77)(422) and 2.268(54)(224). The structure of crimsonite (R1 = 3.57% for 740 Fo > 4σF) contains FeO6 octahedra that share edges to form dimers, which are then linked to other dimers by corner sharing to form chains along [010]. These chains are linked by PO4 tetrahedra yielding sheets parallel to {001}. The sheets are linked to one another via bonds to 8-coordinated Pb2+ atoms with non-stereoactive 6s2 lone-electron pairs.

The new alluaudite-group mineral khrenovite with the ideal, end-member formula Na3Fe3+2(AsO4)3 was found in the Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with aphthitalite-group sulfates, badalovite, calciojohillerite, nickenichite, johillerite, tilasite, svabite, achyrophanite, ozerovaite, pansnerite, arsenatrotitanite, anhydrite, sanidine, hematite, cassiterite, rutile and pseudobrookite. Khrenovite occurs as coarse prismatic crystals up to 0.2 × 0.3 × 0.8 mm and their clusters up to 1 mm across. It is transparent, honey-coloured, red-, orange- or yellow-brown, with vitreous lustre. Khrenovite is brittle, cleavage was not observed. Dcalc is 4.257 g cm–3. Khrenovite is optically biaxial (+), α = 1.825(7), β = 1.834(7), γ = 1.845(7) and 2Vmeas. = 80(10)°. The chemical composition (wt.%, electron-microprobe) is: Na2O 11.47, K2O 1.23, CaO 0.18, MgO 0.01, MnO 4.10, CuO 4.27, ZnO 1.99, Al2O3 0.17, Fe2O3 21.12, SiO2 0.08, P2O5 0.01, V2O5 0.10, As2O5 56.03, SO3 0.02, total 100.78. The empirical formula calculated on the basis of 12 O apfu is (Na2.26K0.16Ca0.02Mn0.35Cu0.33Zn0.15Al0.02Fe3+1.62)Σ4.91(As2.98Si0.01V0.01)Σ3.00O12. Khrenovite is monoclinic, C2/c, a = 12.2394(7), b = 12.7967(5), c = 6.6589(4) Å, β = 112.953(7)°, V = 960.37(10) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data with R1 = 0.0287. Khrenovite is isostructural with other alluaudite-group minerals. Its structural formula simplified to the species-defining constituents is A(1)NaA(2)’NaM(1)NaM(2)Fe3+2(TAsO4)3. The mineral is named in honour of the Russian volcanologist and geologist Anatoly Petrovich Khrenov (1946–2016).

An occurrence of yellowish green to green dufrenite in iron-formation from Proterozoic metamorphites on Kangnas farm near Aggeneys, Bushmanland, South Africa is described. The mineral formed by reaction between iron oxides and hydroxides and a phosphate, probably apatite. It was identified by its characteristic X-ray diffraction pattern, but microprobe analyses presented here indicate that the chemical compositions are extremely variable.

Microprobe and X-ray investigation of a mineral occurring with breithauptite, nickeline, and other arsenides in the naujaite at Igdlúnguaq, Ilímaussaq alkaline massif, S. Greenland, shows that this mineral, which was formerly misidentified as ‘maucherite’, is a westerveldite (Fe0·85Ni0·15)As, of much iron-richer composition than the nickeloan westerveldites from the only two other known occurrences of this mineral. Westerveldite from Igdlúnguaq was presumably formed by reaction of nickeline with iron-rich solutions under conditions of reheating at temperatures of about 450° C and under partial pressures of arsenic below those necessary to stabilize nickeline. Sulphur-bearing löllingite occurs as exsolution blades in the westerveldite. Iron-rich nickeline, up to a composition (Ni0·82Fe0·18)As0·95Sb0·05, was presumably formed by recrystallization of nickeline in the transition stage just before this mineral became unstable and was replaced by westerveldite.