Zoisite-(Pb), a New Orthorhombic Epidote-Related Mineral from the Jakobsberg Mine, Värmland, Sweden, and Its Relationships with Hancockite

The new mineral zoisite-(Pb), ideally CaPbAl3(SiO4)(Si2O7)O(OH), was discovered in a sample from the Jakobsberg manganese-iron oxide deposit, Värmland, Sweden. Zoisite-(Pb) is found as pale pink subhedral prisms elongated on [010], up to 0.3 mm in size, associated with calcite, celsian, diopside, grossular, hancockite, hyalophane, native lead, phlogopite, and vesuvianite. Associated feldspars show one of the highest PbO contents (~7–8 wt%) found in nature. Electron-microprobe analysis of zoisite-(Pb) point to the empirical formula (Ca1.09Pb0.86Mn2+0.01Na0.01)∑1.97(Al2.88Fe3+0.10Mn3+0.04)∑3.02Si3.00O12(OH)1.00. The eight strongest diffraction lines [dobs, Iobs, (hkl)] are 8.63 s (101), 8.11 mw (200), 4.895 m (011), 4.210 m (211), 3.660 s (112, 311), 3.097 mw (312), 2.900 s (013), and 2.725 m (511). Zoisite-(Pb) is isostructural with zoisite and its crystal structure was refined up to R1 = 0.0213 for 2013 reflections with Fo > 4σ(Fo). Pb shows a stereochemically active lone pair leading to a lopsided distribution of its coordinating oxygens. A full chemical and Raman characterization of zoisite-(Pb) and of the Pb-bearing epidote hancockite is reported, together with an improved crystal structural model of hancockite, refined up to R1 = 0.0254 for 2041 reflections with Fo > 4σ(Fo). The effects of the incorporation of Pb in the crystal structure of zoisite-(Pb), hancockite, and related synthetic and natural phases are described and discussed.

Aqua Traiana, a Roman Infrastructure Embedded in the Present: The Mineralogical Perspective

Construction materials from the internal ducts of Aqua Traiana, a still operative Roman aqueduct built in 109 AD to supply water to Rome, were characterized by optical microscopy (OM), scanning electron microscopy (SEM-EDS), X-ray powder diffraction (XRPD) and electron microprobe analysis (EMPA). Petrographic analysis and XRPD revealed that mortar aggregates are compatible with Vitruvius’ harena fossicia and allowed the distinction of the original mortars from those of the 17th-century papal restoration. The first showed an amorphous binder while the latter have a typical lime binder. By SEM-EDS and EMPA, the microstructure of mortar aggregates was analyzed and the composition of specific minerals quantified. Microanalysis testifies the Romans’ great expertise in the selection of pozzolanic building materials, giving evidence of the possible use of local tuffs from the Sabatini Volcanic District. It also confirms the exploitation of red pozzolan from the Roman Magmatic Province, specifically from the Alban Hills district. OM also proves a high compatibility with local supplies for bricks and cocciopesto. Of these, the first were fired at moderately low temperature, while the latter show an amorphous binder as in the original Trajan mortars. All building materials thus stand for similar technological choices and a coeval production.

Native Gold in the Chudnoe Au-Pd-REE Deposit (Subpolar Urals, Russia): Composition, Minerals in Intergrowth and Genesis

Composition of native gold and minerals in intergrowth with rhyolites of the Chudnoe Au-Pd-REE deposit (Subpolar Urals, Russia) was studied using optical microscopy, scanning electron microscopy, and electron microprobe analysis. Five varieties of native gold have been identified, based on the set of impurity elements and their quantities, and on intergrown minerals. Native gold in rhyolites from the Ludnaya ore zone is homogeneous and contains only Ag (fineness 720‰, type I). It is in intergrowth with fuchsite or allanite and mertieite-II. In rhyolites from the Slavnaya ore zone, native gold is heterogeneous, has a higher fineness, different sets and contents of elements: Ag, Cu, 840–860‰ (type II); Ag, Cu, Pd, 830–890‰ (III); Ag, Pd, Cu, Hg, 840–870‰ (IV). It occurs in intergrowth with fuchsite, albite, and mertieite-II (type II), or albite, quartz, and atheneite (III), or quartz, albite, K-feldspar, and mertieite-II (IV). High fineness gold (930–1000‰, type V) with low contents of Ag, Cu, and Pd or their absence occurs in the form as microveins, fringes and microinclusions in native gold II–IV. Tetra-auricupride (AuCu) is presented as isometric inclusions in gold II and platelets in the decay structures in gold III and IV. The preliminary data of a fluid inclusions study showed that gold mineralization at the Chudnoe deposit could have been formed by chloride fluids of low and medium salinity at temperatures from 105 to 230 °C and pressures from 5 to 115 MPa. The formation of native gold I is probably related to fuchsitization and allanitization of rhyolites. The formation of native gold II-V is also associated with the same processes, but it is more complicated and occurred later with a significant role of Na-, Si-, and K-metasomatism. The presence of Pd and Cu in the ores and Cr in fuchsite indicates the important role of mafic-ultramafic magmatism.

Petrology and mineralogy of the Viñales meteorite, the latest fall in Cuba

The new Cuban chondrite, Viñales, fell on February first, 2019 at Pinar del Rio, northwest of Cuba (22°37′10″N, 83°44′34″W). A total of about 50–100 kg of the meteorite were collected and the masses of individual samples are in a range 2–1100 g. Two polished thin sections were studied by optical microscope, Raman spectroscopy and electron microprobe analysis in this study. The meteorite mainly consists of olivine (Fa24.6), low-Ca pyroxene (Fs20.5), and troilite and Fe-Ni metal, with minor amounts of feldspar (Ab82.4-84.7). Three poorly metamorphosed porphyritic olivine-pyroxene and barred olivine chondrules are observed. The homogeneous chemical compositions and petrographic textures indicate that Viñales is a L6 chondrite. The Viñales has fresh black fusion crust with layered structure, indicating it experienced a high temperature of ∼1650°C during atmospheric entry. Black shock melt veins with width of 100–600 μm are pervasive in the Viñales and olivine, bronzite, and metal phases are dominate minerals of the shock melt vein. The shock features of major silicate minerals suggest a shock stage S3, partly S4, and the shock pressure could be >10 GPa.

Garnet-Vesuvianite Equilibrium in Rodingites from Dobšiná (Western Carpathians)

Intensively metasomatized rocks from serpentinized ultramafic tectonic fragments in Dobšiná, Western Carpathians, consist of typical rodingite mineral association: hydrated garnet, vesuvianite, diopside and clinochlore. Electron microprobe analysis (EMPA) and Micro-Raman analyses of the main minerals evidence complex mineralogical evolution and variable mineral chemistry. Garnet solid solution is dominated by grossular-andradite series, which demonstrates a significant degree of hydration, mainly for grossular rich garnet cores. Garnet is locally enriched in TiO2 (up to 13 wt%), possibly indicating a chemical relic of a Ti-oxide mineral. Younger, andradite-richer garnet rims demonstrate a low degree of hydration, suggesting a harder incorporation of an (OH)− anion into its crystal structure. Garnet chemical variations display an ideal negative correlation between Al and (Fe3+ + Ti). The most recent mineral phase is represented by euhedral vesuvianite (± chlorite), which crystallizes at the expense of the garnet solid solution. This reaction shows a well-equilibrated character and indicates a high extent of rodingitization process. Chlorite thermometry models suggest an average temperature of late rodingite (trans) formation of about 265 °C.

Perrierite-(Ce) from the Laacher See tephra, Eifel, Germany, and the modular character of the chevkinite group of minerals

Perrierite-(Ce) crystals from ejecta of the Laacher See volcano, Eifel, in Germany were studied by X-ray single-crystal diffraction and electron microprobe analysis. The composition and crystal structure of this sample is discussed in relation to the known properties of the chevkinite group minerals and related synthetic compounds. Taking into account the modular character of the chevkinite minerals, based on a rutile and a silicate module, the preferred formation of either the perrierite or the chevkinite structure type is correlated with the formal charge of the rutile and silicate modules. The rutile module is expected to carry a negative charge, compensated by a positive charge of the silicate module. On average, the charge modulus is observed to be larger for the chevkinite-type module stacking. It can drop to zero in perrierite-type structures rich in Sr or Ca. In such cases, it is generally not expected to rise above two. The perrierite-(Ce) described in this study crystallizes in space group C2/m. The anisotropic oxygen and rare-earth element displacements observed in this crystal indicate a local domain structure of $$P2_1/a$$ P 2 1 / a symmetry, when compared to the $$P2_1/a$$ P 2 1 / a symmetry of the synthetic perrierite $$\hbox {La}_4\hbox {Mg}_2\hbox {Ti}_3\hbox {O}_8(\hbox {Si}_2\hbox {O}_7)_2$$ La 4 Mg 2 Ti 3 O 8 ( Si 2 O 7 ) 2 .

Crystal Chemistry of Alkali–Aluminum–Iron Sulfates from the Burnt Mine Dumps of the Chelyabinsk Coal Basin, South Urals, Russia

Technogenic steklite, KAl(SO4)2, and unnamed mineral phase (K,Na)3Na3(Fe,Al)2(SO4)6 from burnt dumps of the Chelyabinsk Coal Basin have been investigated by single-crystal X-ray diffraction and electron microprobe analysis. Steklite is trigonal, space group P3¯, a = 4.7277(3), c = 7.9871(5) Å, V = 154.60(2) Å3. The crystal structure was refined to R1 = 0.026 (wR2 = 0.068). It is based upon the [Al(SO4)2]− layers formed by corner sharing of SO4 tetrahedra and AlO6 polyhedra. The anionic [Al(SO4)2]− layers are parallel to the (001) plane and linked via interlayer K+ ions. The regular octahedral coordination of Al is observed that distinguishes technogenic steklite from that found in Tolbachik fumaroles. The (K,Na)3Na3(Fe,Al)2(SO4)6 phase is trigonal, space group R3¯, a = 13.932(2), c = 17.992(2) Å, V = 3024.4(7) Å3, R1 = 0.073 (wR2 = 0.108). The crystal structure is based upon the anionic chains [(Fe,Al)(SO4)3]3− running parallel to the c axis and interconnected via K+ and Na+ ions. There are no known minerals or synthetic compounds isotypic to (K,Na)3Na3(Fe,Al)2(SO4)6, due to the presence of separate K and Na sites in its structure.

Rüdlingerite, Mn2+2V5+As5+O7·2H2O, a New Species Isostructural with Fianelite

The new mineral species rüdlingerite, ideally Mn2+2V5+As5+O7·2H2O, occurs in the Fianel mine, in Val Ferrera, Grisons, Switzerland, a small Alpine metamorphic Mn deposit. It is associated with ansermetite and Fe oxyhydroxide in thin fractures in Triassic dolomitic marbles. Rüdlingerite was also found in specimens recovered from the dump of the Valletta mine, Canosio, Cuneo, Piedmont, Italy, where it occurs together with massive braccoite and several other As- and V-rich phases in richly mineralized veins crossing the quartz-hematite ore. The new mineral displays at both localities yellow to orange, flattened elongated prismatic, euhedral crystals measuring up to 300 μm in length. Electron-microprobe analysis of rüdlingerite from Fianel gave (in wt%): MnO 36.84, FeO 0.06, As2O5, 25.32, V2O5 28.05, SiO2 0.13, H2Ocalc 9.51, total 99.91. On the basis of 9 O anions per formula unit, the chemical formula of rüdlingerite is Mn1.97(V5+1.17 As0.83Si0.01)Σ2.01O7·2H2O. The main diffraction lines are [dobs in Å (Iobs) hkl]: 3.048 (100) 022, 5.34 (80) 120, 2.730 (60) 231, 2.206 (60) 16-1, 7.28 (50) 020, 2.344 (50) 250, 6.88 (40) 110, and 2.452 (40) 320. Study of the crystal structure showcases a monoclinic unit cell, space group P21/n, with a = 7.8289(2) Å, b = 14.5673(4) Å, c = 6.7011(2) Å, β = 93.773(2)°, V = 762.58(4) Å3, Z = 4. The crystal structure has been solved and refined to R1 = 0.041 on the basis of 3784 reflections with Fo > 4σ(F). It shows Mn2+ hosted in chains of octahedra that are subparallel to [-101] and bound together by pairs of tetrahedra hosted by V5+ and As5+, building up a framework. Additional linkage is provided by hydrogen-bonding through H2O coordinating Mn2+ at the octahedra. One tetrahedrally coordinated site is dominated by V5+, T(1)(V0.88As0.12), corresponding to an observed site scattering of 24.20 electrons per site (eps), whereas the second site is strongly dominated by As5+,T(2)(As0.74V0.26), with, accordingly, a higher observed site scattering of 30.40 eps. The new mineral has been approved by the IMA-CNMNC and named for Gottfried Rüdlinger (born 1919), a pioneer in the 1960–1980s, in the search and study of the small minerals from the Alpine manganese mineral deposits of Grisons.