Recommended Nomenclature for the Sapphirine and Surinamite Groups (Sapphirine Supergroup)

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 rhonite (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, rhonite, makarochkinite), Fe(3+) (wilkinsonite, dorrite, hogtuvaite) 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 hogtuvaite, makarochkinite and khmaralite. Classification at the fifth level is based on X(Mg) = Mg/(Mg + Fe(2+)) at the M sites (excluding the two largest 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 (X(mg) \u3e 0.5), or Fe(2+)-dominant (X(Mg) \u3c 0.5), at these M sites. However, X(mg) ranges from 1.00 to 0.03 in material described as rhonite, i.e. there are two species present, one Mg-dominant, the other Fe(2+)-dominant. Three other potentially new species are a Mg-dominant analogue of wilkinsonite, rhonite in the Allende meteorite, which is distinguished front rhonite and dorrite in that Mg rather than Ti or FC(3+) is dominant at M7, and an Al-dominant analogue of sapphirine, in which Al \u3e Si at the two most polymerized T sites vs. Al \u3c Si in sapphirine. Further splitting of the supergroup based on occupancies other than those specified above is not recommended

IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 53

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Loving work: drawing attention to pleasure and pain in the body of the cultural worker

In this article, we present our current research into the body and mind at work, with a particular focus on experiences and implications of enjoyment and love of work within the culture sector. This research is developed through the project Manual Labours that explores the historical conditioning between the body and mind in the so-called immaterial labour conditions. The project aims to identify positive and negative affective labour and the role that physical relationships to work can have in helping conceptualise current working conditions. The enjoyment of work leads to complex differentiations between work and life. This article explores the implications of exploitative labour conditions as self-employed or salaried passionate workers are internalising and developing a sense of ‘un-alienated’ ownership over their wage labour

Stochastic association of neighboring replicons creates replication factories in budding yeast

Peer reviewedPublisher PD

Nuovi minerali italiani. Le approvazioni 2017

La grande complessità geologica della nostra penisola è all'rogine del grande numero di specie mineralogiche nuove descritte per la prima volta al mondo in Italia. Nel corso del 2017, altre nuove specie con località tipo italian, descritte brevemente in questo articolo, sono state approvate dalla Commission on New Minerals, Nomenclature and Classification dell'International Mineralogical Association

The crystal-chemistry of aenigmatite revisited: electron microprobe data, structure refinement, and Mössbauer spectroscopy of aenigmatite from Vesterøya (Norway)

The structure of an untwinned aenigmatite crystal from Vesterøya, Vestfold district, Norway, having a composition (Na3.73 Ca0.27)∑=4.00 (Fe2+8.55 Ti2.10 Mg0.46 Fe3+0.40 Mn0.40 Ca0.06 Zn0.01 Zr0.01) ∑=11.99 (Si11.10 Al0.64 Fe3+0.26) ∑=12.00 O40 was refined in space group P1 to give R1 0.0277 for 5515 unique reflections with Fo > 4σ(Fo) and 0.0324 for all 6145 unique data; GooF 1.124. Cell parameters are a = 10.415(1), b = 10.840(1), c = 8.931(1) Å, α = 105.107(4), β = 96.610(5), γ = 125.398(4)° and V = 746.8(1) Å3. Mössbauer spectroscopy of a bulk sample gave Fe3+/Fetot = 0.12(1) whatever was the initial fitting model, and IVFe3+/Fetot = 0.04(2), which is consistent with IVFe3+/Fetot = 0.018(1) obtained from occupancy of T3, the only T site to have Fe. Ti is fully ordered at M7, the site with the most shared edges, whereas VIFe3+ is mostly ordered at the smallest M sites (M1 and M2), consistent with what is reported in related minerals of the sapphirine group. Ca is ordered at M8, one of the two 8-coordinated sites. Bond lengths and bond-valence sums suggest that T2 and T4 are occupied by Si only, and that T1 and T3 have the highest proportion of Al. Ordering of Ai3+ and Fe3+ at T3 could be related to Ca being ordered at M8, because M8 is linked with T3 through four oxygen anions, more than M8 with any other T site. Thus, one of the four substitutions proposed for aenigmatite, Ca + IVAl ⇔ Na + IVSi, could be operating at a local scale. Since (IVAl + IVFe3+) exceeds Ca, there must be other substitutions for incorporating Al and Fe3+. Two of the four proposed substitutions, VIFe2+ + IVSi ⇔ VIFe3+ + IVAl and VIFe2+ + IVSi ⇔ VIFe3+ + IVFe3+, are consistent with the compositional and Mössbauer data, but the Ti content of 2 per 28 cations rules out incorporation of VIFe3+ in a wilkinsonite component, Na4Fe2+8Fe2+4Si12O40

Crystal structure of turneaureite and crystal-chemical relationships among the minerals of the svabite subgroup (apatite supergroup)

Minerals of the apatite supergroup have the general formula M12M23(TO4)3X. Within the apatite supergroup, the triad svabite – johnbaumite – turneaureite represents one of the rare cases in which three natural end-members are known corresponding to three different X– anions, i.e., svabite, Ca5(AsO4)3F, johnbaumite, Ca5(AsO4)3(OH), and turneaureite, Ca5(AsO4)3Cl. The only other known case is represented by the eponymous series of calcium phospates fluorapatite – hydroxylapatite – chlorapatite (Pasero et al., 2010). We present here the results of a combined chemical (electron microprobe) and structural (single crystal Xray diffraction) study of turneaureite, which follows similar studies carried out on johnbaumite (Biagioni & Pasero, 2013) and svabite (Biagioni et al., 2016). This allows us to make a comparative analysis of the crystal-chemical features of the three calcium arsenate minerals with the apatite structure. The studied sample of turneaureite comes from Nordmark, Värmland, Sweden. Electron microprobe analyses resulted in the following empirical formula: (Ca4.82Mn0.17Ba0.02Sr0.01)(As2.94P0.02S0.02Si0.01)O12 [Cl0.47(OH)0.42F0.11]. The crystal structure of turneaureite was refined in the space group P63/m to R1 = 0.0180, wR2 = 0.0475 for 716 independent reflections, with a = 9.9218(3), c = 6.8638(2) Å. The crystal structure of turneaureite was compared with those of johbaumite (sample from the Jakobsberg mine) and of svabite (sample from the Harstigen mine). The samples of all three minerals originate from three neighbouring Långban-type deposits in the county of Värmland. The geometry of the coordination polyhedra is similar in these three minerals of the savbite subgroup. M1Ca atoms are nine-fold coordinated in tri-augmented trigonal prisms, M2Ca2 atoms are sevenfold coordinated in pentagonal bipyramids, and TAs atoms are tetrahedrally coordinated. Also average bond distances are quite similar in the three structures (johnbaumite, svabite, turneaureite, in Å: = 2.586, 2.586, 2.579; = 2.480, 2.485, 2.529; = 1.671, 1.674, 1.678). There is, however, a relevant difference in the z fractional coordinate of X– anionic position (0, 0, z). In turneaureite chlorine lies at z = 0.319, with an additional mixed-occupancy (OH/F/Cl) site at z = 1/4. In johnbaunite the hydroxyl group lies at z = 0.216, with no additional site. In svabite fluorine lies at z = 1/4, with an additional, mixed-occupancy (F/OH) site at z = 0.195. This results in different Ca2–X bond distances in the three minerals, in keeping with the variable nature of the X– anion