Description and recognition of potassic-richterite, an amphibole supergroup mineral from the Pajsberg ore field, Värmland, Sweden

Potassic-richterite, ideallyAKB(NaCa)CMg5TSi8O22W(OH)2, is recognized as a valid member of the amphibole supergroup (IMA-CNMNC 2017\u2013102). Type material is from the Pajsberg Mn-Fe ore field, Filipstad, V\ue4rmland, Sweden, where the mineral occurs in a Mn-rich skarn, closely associated with mainly phlogopite, jacobsite and tephroite. The megascopic colour is straw yellow to grayish brown and the luster vitreous. The nearly anhedral crystals, up to 4\ua0mm in length, are pale yellow (non-pleochroic) in thin section and optically biaxial ( 12), with \u3b1 = 1.615(5), \u3b2 = 1.625(5), \u3b3 = 1.635(5). The calculated density is 3.07\ua0g\ub7cm 121. VHN100is in the range 610\u2013946. Cleavage is perfect along 110. EPMA analysis in combination with M\uf6ssbauer and infrared spectroscopy yields the empirical formula (K0.61Na0.30Pb0.02) 110.93(Na1.14Ca0.79Mn0.07) 112(Mg4.31Mn0.47Fe3+0.20) 115(Si7.95Al0.04Fe3+0.01) 118O22(OH1.82F0.18) 112for a fragment used for collection of single-crystal X-ray diffraction data. The infra-red spectra show absorption bands at 3672\ua0cm 121and 3736\ua0cm 121for the \u3b1 direction. The crystal structure was refined in space group C2/m to R1 = 3.6% [I\ua0> 2\u3c3(I)], with resulting cell parameters a = 9.9977(3) \uc5, b = 18.0409(4) \uc5, c = 5.2794(2) \uc5, \u3b3 = 104.465(4)\ub0, V = 922.05(5) \uc53and Z = 2. The A and M(4) sites split into A(m) (K+), A(2/m) (Na+), A(2) (Pb2+), and M(4\u2032) (Mn2+) subsites, respectively. The remaining Mn2+is strongly ordered at the octahedrally coordinated M(2) site, possibly together with most of Fe3+. The skarn bearing potassic-richterite formed at peak metamorphism, under conditions of low SiO2and Al2O3activities and relatively high oxygen fugacities

The Rare Earth Elements: demand, global resources, and challenges for resourcing future generations

The rare earth elements (REE) have attracted much attention in recent years, being viewed as critical metals because of China’s domination of their supply chain. This is despite the fact that REE enrichments are known to exist in a wide range of settings, and have been the subject of much recent exploration. Although the REE are often referred to as a single group, in practice each individual element has a specific set of end-uses, and so demand varies between them. Future demand growth to 2026 is likely to be mainly linked to the use of NdFeB magnets, particularly in hybrid and electric vehicles and wind turbines, and in erbium-doped glass fiber for communications. Supply of lanthanum and cerium is forecast to exceed demand. There are several different types of natural (primary) REE resources, including those formed by high-temperature geological processes (carbonatites, alkaline rocks, vein and skarn deposits) and those formed by low-temperature processes (placers, laterites, bauxites and ion-adsorption clays). In this paper, we consider the balance of the individual REE in each deposit type and how that matches demand, and look at some of the issues associated with developing these deposits. This assessment and overview indicate that while each type of REE deposit has different advantages and disadvantages, light rare earth-enriched ion adsorption types appear to have the best match to future REE needs. Production of REE as by-products from, for example, bauxite or phosphate, is potentially the most rapid way to produce additional REE. There are still significant technical and economic challenges to be overcome to create substantial REE supply chains outside China

Prehistory of an enigmatic mineral: hisingerite

According to most sources, the type locality for the hydrous iron silicate mineral hisingerite is Riddarhyttan, Västmanland, Sweden, first reported in 1828. However, it was described by A.F. Cronstedt as early as 1751 from Väster Silvberg, Dalarna (under the name “kolspeglande järnmalm”), and in 1810 by W. Hisinger from the Gillinge iron mine, Södermanland (“svart stenart”, later “gillingit”). J. Berzelius introduced the presently valid species name (originally spelt “hisingrit”) in 1819. Potential type materials are preserved by the Swedish Museum of Natural History, from Gillinge and Riddarhyttan. A Hisinger specimen from Gillinge has recently been analysed and was shown to contain associated potassic-hastingsite, magnetite and fayalite that explain the previously observed aluminium contents and high density for “gillingit”, compared to pure hisingerit

Raman spectroscopy as a tool in mineral discoveries

Preliminary investigations of unknown minerals are frequently based on physical and optical observations, chemical analysis and collection of powder X-ray diffraction data. At the Swedish Museum of Natural History, laser Raman micro-spectrometry has been adopted as a standard method, which led to discoveries that otherwise might have been unnoted. The new mineral garpenbergite (IMA2020-099), with formula Mn6□AsSbO10(OH)2, is found at the Garpenberg Zn-Pb-Ag deposit, Dalarna (Dalecarlia), Sweden. Preliminary data indicated a close relationship to manganostibite, ideally Mn7AsSbO12. The two minerals are not easily distinguished using routine procedures, because of almost identical powder patterns and similar chemical compositions. In the Raman spectra, a characteristic feature, with distinct bands at 3647 and 3622 cm-1 related to OH-stretching vibration modes, appears for garpenbergite only. Structural refinement from single-crystal X-ray diffraction data yielded an orthorhombic unit cell, with a = 8.6919(10), b = 18.927(3), c = 6.1110(6) Å for Z = 4. The crystal structure is distinct by the presence of a vacancy, corresponding to an octahedrally coordinated Mn2+ site in manganostibite (Moore, 1970), and by incorporation of protons via the exchange mechanism Mn2+ + 2O2- → □ + 2(OH)- that leaves the space-group symmetry, Ibmm, invariant. Parahibbingite (IMA2020-038a) was recently approved, with the Karee mine in the Bushveld complex, South Africa, as type locality. This mineral, with formula Fe2+2(OH)3Cl, has independently also been identified on samples of corrosion crust from weathered fragments of the Muonionalusta iron meteorite, collected in the Kitkiöjärvi area, Pajala, in northernmost Sweden. From initial energy-dispersive X-ray microanalysis, it was identified as hibbingite or possibly another polymorph of Fe2+2(OH)3Cl , and the identity with the rhombohedral β-form was then confirmed with Raman spectroscopy, when compared with data for the synthetic analogue. A subsequent refinement of the crystal structure, including the hydrogen positions, from single-crystal diffraction data gave a = 6.9362(4), c = 14.6730(11) Å with Z = 6 for the R-3m unit cell, in good agreement with previous Rietveld refinement of synthetic material and corrosion products from artefacts. Magnussonite, ca. Mn10As6O18OH2, is a rare arsenite mineral with inferred cubic crystal symmetry that has been the subject of several studies. Brattforsite, ideally Mn19(AsO3)12Cl2 (IMA2019-127), has a similar structural topology as magnussonite and is a monoclinic bona fide Cl-analogue . The close relationship between the two minerals is supported by their resemblance in the Raman spectra overall, but there is also a distinct shift (ca. 30 cm-1) in the bands originating from As-O stretching in the (AsO3)3- groups, related to differences in mean bond lengths between the corresponding atoms.    

Speaking of anniversaries: Who was the first modern mineralogist?

Mineralogy is among the oldest sciences and a core discipline of geology. Already in the Neolithic period, the recognition and use of various minerals was important knowledge for humans. Writers of the Antiquity on the subject, Theophrastus and Pliny the Elder, treated rocks and minerals from a natural-philosophical point of view. Polymaths like Avicenna (Persia) and Shen Kuo (China) in the 11th century AD also documented the minerals known to exist then. European authors of the Renaissance, with Georgius Agricola as the foremost, used the intrinsic physical properties of minerals to describe and classify them in systematic way, an approach that essentially established mineralogy as a science. In Sweden, there was little development in the field before the 18th century (a notable exception is the contributions of Urban Hjärne). During the Age of Liberty*, works relating to various aspects of minerals, by natural scientists like Johan Gottschalk Wallerius, Henrik Teofil Scheffer, Carl Linnaeus and Torbern Bergman, came to have a wide influence, far beyond Sweden’s borders. Among the mineralogists active in this dynamic period, Axel Fredrik Cronstedt stands out as an exeptionally innovative and forsighted character

Crystal structure and composition of hiärneite, Ca2Zr4Mn3+SbTiO16, and constitution of the calzirtite group

The crystal structure of hiärneite has been refined from single-crystal X-ray diffraction data (λ = 0.71073 Å) on type material from Långban, Värmland, Sweden. The refinement converged to R1 = 0.046 based on 1073 reflections with F2 > 4σ(F2). The tetragonal unit cell, space group I41/acd, has the parameters a = 15.2344(6) Å and c = 10.0891(6) Å with Z = 8. The mineral is isostructural with calzirtite, ideally Ca2Zr5Ti2O16, with a structural topology derived from fluorite. In hiärneite, Mn3+ is ordered at a 4- to 8-fold coordinated site (with a distorted polyhedral coordination figure), without the atom splitting encountered at the corresponding Zr-dominated site of calzirtite. The end-member formula for hiärneite is established as Ca2Zr4Mn3+SbTiO16. The calzirtite group, with calzirtite, hiärneite and tazheranite (cubic ZrO2-x), has been approved by the IMA–CNMNC

Nomenclature of the magnetoplumbite group

A nomenclature classification scheme has been approved by IMA-CNMNC for the magnetoplumbite group, with the general formula A[B12]O19. The classification on the highest hierarchical level is decided by the dominant metal at the 12-coordinated A sites, at present leading to the magnetoplumbite (A = Pb), hawthorneite (A = Ba) and hibonite (A = Ca) subgroups. Two species remain ungrouped. Most cations, with valencies from 2+ to 5+, show strong order over the five crystallographic B sites present in the crystal structure, which forms the basis for the definition of different mineral species. A new name, chihuahuaite, is introduced and replaces hibonite-(Fe)