The use of optical absorption spectroscopy for the study of the changes in local distortions during phase transformations is discussed, with particular reference to the P213-P212121 transition in K2Co2(SO4)3 langbeinite. In order to extend this technique to the study of cobalt-doped cadmium langbeinite, K2Cd2(SO4)3, the consequences of the doping with regard to site occupancies and low signal strength are discussed, and some details of data modelling are considered. The problem of modelling the spectrum of Finero sapphirine is taken as an example, and it is shown that even simple and evidently inadequate models can provide useful information.

The results of optical spectroscopic investigation of the P213-P212121 transition in K2(Cd0.98Co0.02)2(SO4)3 langbeinite are presented. The trigonal splitting of the spin allowed 4T1g(F)-4T1g(P) transition has been determined, and shows a linear increase with increasing temperature in the high temperature cubic phase, and a constant value in the low temperature phase. This is in good agreement with previous structural work on this material, and it is concluded that optical spectroscopy of doped materials can provide useful information about site distortions.

This first report of the occurrence of a kimberlitic rock in Pakistan is supported by its field relations, textures and mineral chemistry. Linear dykes, lenses, conical and pipe-like bodies, plugs and sills intrude non-orogenic, early Jurassic limestone near the SW extremity of an Eocene-emplaced ophiolite on the transform-type Indian plate margin; far away from the stable Precambrian craton. The rock resembles ‘micaceous kimberlites’ petrographically and contains olivine, phlogopite, perovskite, chromian spinel, monticellite, chlorite, serpentine, calcite, apatite, pectolite, clinopyroxene, amphibole, nepheline, magnetite and titanomagnetite. The minerals and their microprobe analyses resemble those of kimberlitic rocks.

Mössbauer spectroscopy and electron microscopy were combined to study one Al-poor anthophyllite and one Al-rich gedrite. TEM show that Al-rich gedrite is not homogeneous and that the complexity of its Mössbauer spectrum is due to sub-microscopic intergrowth of chlorite and lizardite.

Physical, crystal-chemical and absorption spectroscopical properties of blue tourmalines from a new occurrence in the State of Paraiba, Brazil, are described. Refractive indices, birefringence and specific gravity have been determined as ne = 1.615–1.620, no = 1.632–1.640, Δn=−0.017 to −0.020 and 3.04–3.07g/cm3. Microprobe analyses proved the samples to be elbaites, which are relatively Mn-rich and contain 2.1 wt. % CuO and 0.5 wt. % Bi2O3. Lattice constants are ao = 15.854(4) and co = 7.102(1) Å. The blue colour is due to pleochroic absorption bands of Cu2+ and Mn3+ with maxima at 700 and 520 nm respectively.

Basal cleavage faces of apophyllite crystals were etched in the base etchant (dil HF) containing different concentrations of ammonium fluoride as a poisoning salt. At low concentrations, square pyramidal pits formed with their sides parallel to the <100> direction. At higher concentrations, pits with their sides parallel to the <100> direction were formed. The lateral growth of a pit is dependent on pH value of the etching solution. Activation energy for dissolution at a pit (active site) was found to decrease with increasing concentration of poison in the base etchant. The change in orientation of the pit is attributed to adsorption of aqueous complexes having different chemical constitutions which have different directional adsorption sites in apophyllite.

The effects of (OH)/F substitutions on thermally induced reactions in the apophyllite group have been investigated using TGA and DTA methods, supplemented by X-ray diffraction, infra-red and other techniques to identify the products of reaction. The samples studied cover the range between fluorapophyllite and hydroxyapophyllite, and include some unusual ammonium varieties. The presence or absence of fluorine exerts a major control on thermally induced reactions, not only during low-temperature dehydration, but also on high temperature recrystallization reactions up to 900°C+. All apophyllites dehydrate in two stages, the first being loss of a proportion of the water with only minor distortion of the crystal lattice, whereas the second results in total collapse into an amorphous material. Higher fluorine concentrations stabilize the structure, shifting dehydration reactions to higher temperatures, and permitting more water molecules to be lost during the first stage without destruction of the structure. Fluorine is not lost during the second-stage dehydration, as previously believed, but most is retained and influences subsequent recrystallization reactions.

Dehydrated hydroxyapophyllites remain amorphous until ca. 900°C, when high-temperature wollastonite crystallizes. Fluorapophyllites initially form a metastable CaF2.SiO2 phase by 700°C, low-temperature wollastonite by 800°C, both disappearing above 900°C when fluorine loss occurs and high-temperature wollastonite is produced. TGA and DTA provide simple methods of distinguishing between hydroxy- and fluorapophyllites.

Ammonian apophyllites, with up to 25% of the stoichiometric K+ replaced by NH4+ (in the samples studied), can be recognized by their DTA patterns, the endothermic peak for the second stage reaction being significantly reduced, and that for the first, dehydration, stage being correspondingly enhanced. Such samples have weight losses well above the calculated water content, the excess being due to evolution of ammonia. Ammonian varieties also have an extra infra-red absorption band at 1460 cm−1.

Coesite has been found as an inclusion in garnet from the Mengzhong eclogite in Donghai county, northeastern Jiangsu province, eastern China. The host eclogite occurs closely associated with regionally developed gneiss and was formed under P-T conditions of about 810°C and more than 28 kbar.

Ilmenites from alkaline basic dykes in the Gardar province, south Greenland have Zr contents up to 3850ppm and Nb contents up to 1030ppm. These elements substitute for Ti in the octahedral site. These are amongst the highest recorded Zr and Nb contents for ilmenites, giving distribution coefficients (Kdilmenite/matrix) for Zr up to 11.6 and Nb up to 70.3. Fractionation of ilmenite may thus have a dramatic effect on residual Zr and Nb contents. These effects are discussed in relation to the use of trace element tectonomagmatic discrimination diagrams.

High-resolution transmission electron microscopy of biogenic carbonate minerals is hampered by a lack of stability during exposure to the electron beam. However, aragonite in bivalve shells may be successfully imaged using a modification of the ‘minimal-exposure technique’ of Williams and Fisher (1970). Diffraction patterns taken before and after beam exposure indicate that the aragonite remained stable during imaging. The procedure described here should prove useful for further studies of the ultrastructure and/or the diagenesis of biogenic carbonate minerals.

Damaraite, ideally 3PbO.PbCl2, is a new mineral which occurs with jacobsite, hausmannite, hematophanite, native copper, an unnamed Pb-Mo oxychloride, calcite, and baryte, in specimens from the Asis West section of the Kombat mine, Namibia (South West Africa). Damaraite is colourless and transparent with a white streak, and adamantine lustre. It is brittle with an irregular to subconchoidal fracture and a cleavage on (010). The mineral has a low reflectance, a weak bireflectance, barely discernible reflectance pleochroism, from grey to slightly bluish grey in some sections, and is weakly anisotropic. Reflectance data in air and in oil are tabulated. Colour values relative to the CIE illuminant C for the most strongly bireflectant grain are, for R1 and R2 respectively:

It has a VHN50 of 148 (range 145–154) with a calculated Mohs hardness of 3. X-ray powder diffraction studies give the following parameters refined from the powder data: orthorhombic; space group Pma2, Pmam or P21am; a 15.104(1), b 6.891(1), c 5.806 (1)Å; V is 604.3 (4)Å3 and Z = 3. Dcalc 7.84 g/cm3. The strongest six lines of the powder pattern are [d in Å (I) (hkl)]: 2.902 (10) (121,002); 2.766 (10) (510,221); 2.877 (9) (411); 3.164 (6) (401); 3.135 (6) (220); 1.747 (b) (313,721,531). The name is for the Damara sequence which hosts the Kombat deposit.

A calcium-rich ralstonite, forming colourless octahedral crystals up to 2 mm across, occurs in a F-rich assemblage at the Cleveland Mine, northwestern Tasmania. Other minerals present include well-crystallized morinite, gearksutite, vivianite, siderite, K-rich feldspar (adularia), fluorite and quartz. The F-rich assemblage probably formed during greisenization when Na and F-rich magmatic brines reacted with enclosing carbonate host rocks to produce hydrothermal Na-Ca-Mg-bearing solutions. Chemical analysis of the ralstonite-like mineral gave a formula (Na1.47Ca0.52)(Mg1.49Al0.55P0.04)F6 [(OH)0.43O0.36F0.21)].

This differs from the ‘pyrochlore’ formula, due to the substitution of Ca + (OH,O,F) for H2O, in addition to the coupled substitution of Na + Mg for Al in ‘normal’ ralstonites. The Cleveland Mine ralstonite has the highest recorded Ca, Na and Mg contents. While the mineral is likely to be a new species on chemical grounds, single crystal X-ray photographs indicate the structure is disordered, possibly composed of small compositional domains.

Corkite associated with plumbojarosite and goethite occurs in gossan and iron-formation at Black Mountain and Broken Hill, Aggeneys. Electron microprobe analyses indicate that there are two groups of corkite present in the area; one with high Cu and low (PO4)3− and the other with low Cu and high (PO and the other with low Cu and high (PO4)3− contents. This can be explained in terms of the general formula contents. This can be explained in terms of the general formula AB2(XO4)2(OH)6, where the incorporation of divalent ions in the B site is accompanied by the exchange of trivalent anions by divalent ones to retain charge balance. Complete solid-solution is inferred between (SO4)2−and (PO4)3− end members, indicating that the jarosite and beudantite groups form part of the same solid-solution series. The distribution of Zn in corkite also reflects the regional distribution of zinc grades in the area, becoming more zinc-rich from west to east. New X-ray diffraction parameters are also presented which update existing data.

Alvanite is monoclinic P21/n, with a = 17.808(8), b = 5.132(3), c = 8.881(4)Å, and β = 92.11(3)0. The density is 2.49 g/cm3 (meas), 2.492 g/cm3 (calc), Microprobe analysis yielded Al2O3 34.2, FeO 0.3, ZnO 7.6, NiO 4.2, V2O5 27.5, H2O (by difference) 26.2, total = 100.0 wt. %. This leads to the idealized formula (Zn,Ni)Al4(VO3)2(OH)12·2H2O with Z = 2.

The crystal structure of the new mineral kamchatkite, a= 9.741(5), b= 12.858(6), c=7.001(3)Å, space group Pna21, Z = 4, has been determined through direct methods using 1430 intensities and refined to a final discrepancy index R = 0.055. It contains (SO4) tetrahedra and Cu octahedra interconnected by oxygen atoms to form an electrostatically neutral three-dimensional arrangement of formula Cu3O[SO4]2 which contains channels parallel to [001]. The channels are not empty but house KCl molecules.

Gold mineralization at the Ashanti Mine occurs in shear zones which are second-order components of a major transcrustal shear zone. However, gold-rich telluride mineralization in veins in the hangingwall of the Obuasi ore zone at Ashanti appears to have post-dated development of the major gold-bearing shear zone. Complex assemblages of goethite, chalcocite, coloradoite, calaverite, sylvanite, kostovite, petzite, stutzite, hessite, altaite, rickardite, weissite and henryite were succeeded by a relatively simple assemblage of altaite-petzite-hessite ± sylvanite ± coloradoite. Precipitation occurred over a temperature range of approximately 220°C to 165°C from a CO2-bearing, low salinity (<5 wt. % NaCl equiv.) fluid under conditions of high ƒo2 and high ƒTe2/ƒS2. Replacement of earlier gold-sulphide mineralization is indicated.

The fluids were introduced during late activation of the Obuasi shear zone, which evolved during the c.2000 Ma Eburnean tectonothermal event that marked the onset of cratonization of the West African shield. The localized and time-specific distribution of the telluride mineralization may be indicative of a late influx of tellurium-rich fluid linked to emplacement of a synorogenic, Cape Coast-type granitoid intrusion.

The occurrence is reported of a saline spring water from Weardale, which compositionally closely resembles other saline waters derived from the Carnmenellis granite, southwest England. The total dissolved solutes achieve approximately 38 000 mg/L, and alkali geothermometers suggest equilibration temperatures of approximately 150°C, equivalent to a depth of 4 km. Using Na, K and Li it is possible to compare the composition of the spring water with those of other spring waters derived from Carboniferous sequences adjacent to the North Pennine Orefield and with published data for fluid inclusions from North Pennine fluorite. These compositional parameters suggest that the ancient mineralizing fluids resemble modern Carboniferous sediment-derived waters and contain a relatively minor component of granite-derived water. Data for Br and Cl indicate that a significant component of the present day Weardale spring waters was probably ultimately derived from organic-rich sedimentary sequences while data for K, Na and Li indicate the importance of a component derived from a permeable granite aquifer. The Weardale springwaters continue to have ‘mineralizing’ potential, in view of the possibility that they may have precipitated quartz or chalcedony during their ascent.

A core of concrete taken from a major road bridge in the Strathclyde Region, Scotland, has been subjected to an applied mineralogical investigation, which involved stable isotope analysis, petrography, X-ray diffraction and scanning electron microscopy.

The structure is actively undergoing severe degradation due to mineral growth which is related to chemical reactions between the concrete and pore fluid. The physical growth of minerals causes disfigurement and structural weakening.

Pyrite and pyrrhotine hosted by dolerite aggregate appear to have been oxidized, providing sulphate for the deposition of ettringite and minor gypsum, in spheroidal cavities within the cement paste. The rainwater which passes through the structure mobilising sulphate from original gypsum in the paste and oxidizing the iron sulphides is also involved in the further leaching of elements from the cement paste and in the deposition of calcite. The isotopic values of calcites forming a crust on the concrete and a stalactite under the bridge are similar with δ13C= −19‰ PDB and δ18‰= +16‰ SMOW. We suggest that atmospheric carbon dioxide was the carbon source. The carbon isotopic fractionation of −12‰ from atmospheric carbon dioxide of δ13C= −7‰, (O'Neil and Barnes, 1971) can best be explained as due to a kinetic fractionation related to the hyper-basicity of the pore water. The equilibrium formation temperature of about 45°C calculated from the oxygen isotope values and assuming a δ18O value of meteoric water of −8‰ SMOW, is considered unreasonable. The exceptionally low δ18O values are attributed mainly to reaction kinetics and the calcite inheriting its oxygen, two-thirds from atmospheric carbon dioxide and one third from the meteoric formation water (O'Neil and Barnes, 1971). A δ18O value of atmospheric carbon dioxide of +41‰ SMOW and a δ18O value of meteoric water of −8‰ SMOW, lead to a calculated δ18O value for the calcites of +10‰ SMOW. The calcites analysed have a value of +16‰ and this may be due to partial re-equilibration towards a calculated value of +21‰ for calcite in equilibrium with the meteoric water at 20°C.