Nodules of manganoan fayalite occur in schlieren pegmatities in the vicinity of Strzegom, Lower Silesia. The fayalite, Na0.02(Fe1.812+Mn0.16Mg 0.03)Si0.99O4, is unzoned and non pleochroic. 2Va = 42° a 4.826(3), b 10.500(2), c 6.102(2) A, d130obs. = 2.83 Å, d130calc. = 2.833 Å, D = 4.35 g cm-3, Dcalc. = 4.353 g cm-3. The role of Na+ ions in the fayalite chemistry is discussed. The fayalite underwent multi-stage hydrothermal alteration beginning at the highest temperature (440°C) of homogenization of gaseous-fluid inclusions in quartz adjacent to the fayalite grains. Increase in fO2 and then in PH2O resulted in the formation of magnetite-quartz and Mn-grunerite-magnetite-quartz aggregates within the fayalite grains. The fayalite is mantled by a Mn-greenalite-magnetite rim, Mn-grunerite-magnetite-Mn-minnesotaite zone in a stilpnomelane or greenalite-rich groundmass. The minnesotaite is believed to have formed at the expense of grunerite. Stilpnomelane, the most abundant silicate phase in the rim, is the product of biotite and presumably greenalite alteration at the second stage of increasing Na activity (the crystallization of cleavelandite) in the pegmatites. The fayalite is also heavily altered to iddingsite—a composite mixture of amorphous FeOOH and silica. The iron-hydroxide recrystallized partially to poorly-crystalline goethite.

The transmittance spectra of a synthetic alexandrite recorded along directions parallel to the three crystallographic axes are generally similar, but the observed colour changes along these directions under different light sources are quite different. Calculated hue-angle changes for the colours observed under different pairs of C.I.E. standard illuminants are the largest for light travelling parallel to the a-axis. Therefore, alexandrite should be cut as a gemstone with the top facet oriented parallel to (100) for it to show the most dramatic change in colour.

The Bratteggdalen granogabbro, a relict mass in the Caledonian amphibolites of Vestspitsbergen, shows a series of amphibole development reflecting its thermal history. A brown Ti-rich hornblende occurs as a late magmatic mantling of pyroxene. Low-grade metamorphism (greenschist facies) was accompanied by the development of actinolite from pyroxene; subsequent amphibolite facies metamorphism saw the development of an alkali-rich, blue-green hornblende. The chemical changes in the amphiboles are a succinct illustration of those found in progressive regional metamorphism.

Ilmenite–pyrophanite crystals from a garnet pegmatite dyke from the Upper Codera Valley (Sondrio, Italian Alps) showing exsolutions of titanohematite and columbite-tantalite were investigated by scanning and transmission electron microscopy. The titanohematite precipitates share the same crystallographic orientation of the ilmenite-pyrophanite host, are bean-shaped when observed on sections inclined to the pinacoidal section, and are elongated when observed on sections closer to the prism section, possibly because of their discoidal shape parallel to (001). The columbite-tantalite precipitates form a hexagonal network of needles elongated along ⟨110⟩ of the ilmenite–pyrophanite and titanohematite host. The following crystallographic relationship was established: [100]Col//[001]Ilm; [001]Col//[110]Ilm; , which can be explained in terms of preservation of the oxygen close packing between the ilmenite and columbite structures. The interfaces between any two of the three different phases are coherent but show lattice strain contrast and sometimes dislocations because of their different unit-cell dimensions. On the basis of textural observations, titanohematite is supposed to exsolve first, followed by columbite-tantalite at temperatures below 500°C. The addition of MnO to the Fe2O3–FeTiO3 system is supposed to considerably influence the topology of the related T-X phase diagram and the solubility of Nb2O5 and Ta2O5 in this system.

One of the most important isotopes to be considered for disposal in the proposed UK Geological Disposal Facility (GDF) for higher-activity radioactive wastes will be 99Tc, due to its long half-life, high fission yield and ability to migrate through the geosphere as the pertechnetate ion. Much of the Tc is likely to be in the lower Tc(IV) oxidation state due to the low Eh in the near field. Batch Tc(IV) sorption experiments have been performed from pH 3–13, using 95mTc as a spike, in the presence of quartz, hematite, goethite, plagioclase feldspar, sand and shale. Solutions containing Tc(IV) were prepared at trace concentrations to avoid precipitation of TcO2. Values for the partition coefficient (Rd) were found to range from ∽4 up to ∽2 × 104 cm3 g–1. Rd was heavily dependent on pH in all cases, with the highest values being found in the circumneutral area. These data will inform the performance assessment for the near-field behaviour of technetium in the UK's planned higher-activity wastes GDF. Surface complexation modelling has been performed, fitting the data using both monodentate and bidentate binding models.

Trioctahedral ferromagnesium micas from the Archaean amphibolites of the Kola super-deep borehole (KSDB-3) complex have been compared with those from analogous Archaean surface rocks in an integrated study of their chemical compositions and structural states (using wet chemistry, microprobe, X-ray, Mössbauer and infrared methods). Reports on both the experimental procedure and the crystal chemistry of the trioctahedral micas are given. This has enabled the revision of the assignment of individual infrared (IR) absorption bands for the hydroxyl ion (vOH−), and demonstrated the possibility of determining the content of Mg, Fe2+, R3+; cations and vacancies in the octahedral sheet to within a few hundredths of atomic units on the basis of the infrared and Mössbauer data. Proof was found of the presence of molecular water replacing K+ in the interlayer, which results in anomalous variations in the cell parameters, as the mica structure expands in response to the ingress of H2O. Variations in the degree of non-stoichiometry of the micas is related to the presence of structural H2O and of octahedral M1 vacancies. We found that samples recovered from depth within the borehole display lower degrees of octahedral order than those found in the analogous surface rocks.

Infrared powder-absorption spectra of ten synthetic P21/c pyroxenes with compositions in the clinoenstatite–clinoferrosilite system have been collected at room temperature in the range 50–1500 cm−1. Variations of peak positions as a function of Fe content have been obtained for those vibrational bands whose trend could be followed across the solid solution. Local elastic strains arising from cation substitution have been quantified by means of the autocorrelation function, which gives a measure (Δcorr) proportional to the line width of the IR bands. The structure of clinoenstatite appears to be very homogeneous, whereas Fe-rich pyroxenes have high degrees of local structural hetereogeneities. A positive deviation from linearity of the Δcorr values is observed in the spectral region between 100 and 250 cm−1 and may be indicative of a positive excess enthalpy of mixing of this solid solution. At higher energies the large changes in the phonon spectra as Fe content increases are associated with rotation and deformation of the tetrahedral chains for accommodating the larger cation. The results are compared with similar studies on other chain silicates.

Two hundred years (1750–1950) of earthen architecture represents an important period of construction in the central region of Portugal. Earthen architecture is usually built close to the coast or to rivers and placed in sandy ground. The impact of rising damp is a general problem and efflorescences are a common cause of damage decay. This problem was studied in a building with two types of earthen construction, adobe masonry walls and formed masonry walls. The aim of this research was to characterise the conditions for the appearance and phase transitions of thénardite and mirabilite, and determine how to prevent progression of salt effects in the two types of wall to support future conservation measures. Laboratory capillarity and porosimetry tests with dolomitic air lime mortar and hygrothermal monitoring were pursued along with in situ tests. Visual assessment showed that the progression of salts depends on the composition of the earthen materials. To understand these differences, all crystalline solid phases were analysed by powder X-ray diffraction, and building interior hygrothermal conditions were monitored. An investigation into the influence of surface lime water painting and sacrificial mortar application on the crystallisation of sodium sulfates concluded that these also depend on the wall's composition. Data allowed us to conclude that inside the building the temperature and humidity [relative humidity (RH = 100 pw/p°w > 70)] conditions led to the adobe breakdown by the fast conversion from thénardite to mirabilite. Therefore, contact with wet atmospheres should be avoided and interior hygrothermal conditions should be controlled. Laboratory and in situ tests showed that the environmental conditions of the spaces had effects on the results. The results contribute to understanding of the salt progression and pattern of decay, as well as supporting future recommendations for building conservation, based on the identification of environmental conditions proper to their occurrence.

Feldspar of composition Ca0.2Pb0.8Al2Si2O8 (PbF80An20) was synthesized from melt and subsequently isothermally annealed at T = 960°C for 4 days. In situ HT X-ray powder spectra of PbF80An20 feldspar, triclinic I1̄ at room temperature, were collected in the temperature range 20–800°C, and a displacive continuous ferroelastic transition to a I2/c monoclinic phase was observed. An analysis of the symmetry-required components of the spontaneous strain tensor reveals the second order character (β = 0.46 ± 0.02) of the transition with TC = 680 ± 15°C. A linear coupling was observed between the e4 and e6 components of the spontaneous strain. The transition is analogous to those observed, with increasing temperature, along the join An–SrF and in disordered Na-rich alkali feldspars. A comparison with Ca0.2Sr0.8Al2Si2O8 feldspar (TC = 680°C, McGuinn and Redfern, 1997) shows that PbF80An20 has a higher spontaneous strain (εs = 0.028 in PbF80An20vs 0.020 in Ca0.2Sr0.8Al2Si2O8) and a higher e4 component, possibly related to the higher distortion of the non-tetrahedral polyhedron in lead feldspar.

The crystal structure of a Mn-bearing kilchoanite, Ca2.33Mn0.67Si2O7, orthorhombic, I2cm, a = 11.356(2), b = 5.007(1), c = 21.817(1)Å, Z = 8, was refined using single-crystal X-ray data to an R value of 3.1% for 1725 unique reflections. It is isostructural with kilchoanite, Ca3Si2O7, and shows a partial disorder of Mn and Ca over the four octahedral sites. On a basis of occupancy refinement, the M3 site (〈M3-O〉 = 2.307 Å) contains 0.508Ca and 0.492Mn, and the M4 site (〈M4-O〉 = 2.346 Å) contains 0.822Ca and 0.178Mn, whereas the M1 and M2 sites (〈M1-O〉 = 2.538 Å, (〈M2-O〉 = 2.380 Å) are occupied only by Ca. Substitution of Mn cations for Ca can be interpreted as taking place on the following sites in preferential order: (1) the smaller Ca site; (2) the less distorted Ca site; (3) the Ca site showing a loss in neutrality of formal electrostatic valence. A statistical survey of Si-O-Si angles observed in silicates containing [Si2O7] groups confirms that these angles become smaller with an increase in the coordination number of the bridging oxygen. Oversaturation of electrostatic bond-strength to the bridging oxygen in some groups of the crystal structures with two tetrahedra sharing a vertex (pyro-anion, ), which is caused by increase in the coordination number of the bridging oxygen and/or by T cations with larger charge than 4+, results in longer T-Obr bonds length and in smaller T-Obr-T angles.

Thermodynamic data are constrained by the interrelated thermodynamic equations in addition to the observational measurements and their uncertainties. The consequence is a network of thermodynamic properties that can be evaluated for their internal consistency. In this study, three fluoride minerals that can cause high fluoride concentrations in groundwaters are evaluated for their solubilities and their internal thermodynamic consistency with calorimetric, isopiestic and electrochemical measurements: fluorite, CaF2, cryolite, Na3AlF6, and villiaumite, NaF. This evaluation involves the three solids and 13 aqueous species, the free ions of Ca2+, Na+, Al3+ and F–, and the hydroxido and fluorido complexes of Al3+, and the CaF+ ion pair. For the fluorite–cryolite–villiaumite–aqueous species network, the number of components is minimal, and the solubility studies are mostly of high quality. Re-evaluations of original data using PHREEQC helps to broaden the quantitative evaluation of thermodynamic properties and to resolve apparent discrepancies. A check on this thermodynamic network shows that through a careful appraisal of the literature, a highly consistent set of values can be derived. The resultant infinite-dilution solubility-product constants at 25°C and 1 bar are: for fluorite solubility, logKsp = –10.57 ± 0.08; for cryolite solubility, logKsp = –33.9 ± 0.2; and for villiaumite solubility, logKsp = –0.4981 ± 0.003.

A new mineral kalithallite, K3Tl3+Cl6⋅2H2O, was found in an active fumarole belonging to the Northern fumarole field at the First scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Kalithallite is a product of the relatively low-temperature (70–150°C) interactions involving high-temperature sublimate minerals, volcanic gas and atmospheric water vapour. The associated minerals are cryobostryxite, KZnCl3⋅2H2O, halite, sylvite, opal and gypsum. Kalithallite forms lamellar to tabular crystals up to 5 × 30 × 40 μm combined in open-work aggregates up to 1 mm across. It is transparent, colourless in individuals and white to pale cream coloured or pale beige in aggregates, with vitreous lustre. Dcalc = 3.01 g cm–3. Kalithallite is optically uniaxial (–), ɛ = 1.656(3) and ω = 1.662(3). The chemical composition (wt.%, electron-microprobe data, H2O calculated by stoichiometry) is: K 17.72, Zn 0.85, Tl 38.76, Cl 35.91, H2Ocalc 5.99, total 99.23. The empirical formula calculated on the basis of K+Zn+Tl+Cl = 10 apfu is K2.72Zn0.06Tl1.14Cl6.08⋅2H2O. Kalithallite is tetragonal, I4/mmm, a = 15.9333(5), c = 18.1088(7) Å, V = 4595.2(4) Å3 and Z = 14. The strongest reflections of the powder X-ray diffraction (XRD) pattern [d,Å(I)(hkl)] are: 5.98(100)(202); 5.64(36)(220); 3.984(20)(400); 3.528(30)(224); 3.315(22)(422); 2.890(15)(334); and 2.817(24)(206, 440). Kalithallite is isotypical to synthetic K3Tl3+Cl6⋅2H2O. The crystal structure was refined from the powder XRD data using the Rietveld method, RBragg = 0.55%, Rp = 0.56%, and Rwp = 0.75%. The structure contains Tl3+Cl6 octahedra and K-centred polyhedra of three types: KCl8, KCl8(H2O) and KCl7(H2O)2. The mineral is named as a kalium–thallium ordered compound.

The labour of tracing the history of the Red Silver Ores, of collating the literature, and of tabulating the crystalline forms previously observed, has been, to a large extent, rendered unnecessary by the memoir published by E. Rethwisch (Neues Jahrbuch für Mineraloqie, Beilage Band iv. (1886), pp. 31-109), under the title "Beiträge zur mineralogischen und chemischen Kenntniss des Rothgültigerzes."

In 1929 Väiyrynen discovered a chalcopyrite-bearing pyrrhotine deposit at the village of Luikonlahti, 30 km. NW. of the Outokumpu mine. This occurrence is associated with a complex of serpentine, quartzites, phyllites, dolomites, and diopside-tremolite-roeks, together with penetrating granites, aplites, and pegmatites. The rock association thus closely resembles that of the Outokumpu ore-field.