Girdite, H2Pb3(TeO3)TeO6 is white, H = 2, D = 5.5. Crystals are complexly twinned and appear monoclinic domatic. The X-ray cell is a = 6.241Å, b = 5.686, c = 8.719, β = 91°41′; Z = 1.

Oboyerite is H6Pb6(TeO3)3(TeO6)2 · 2H2O. H = 1.5, D = 6.4. Crystals appear to be triclinic but are too small for X-ray work.

Fairbankite PbTeO3 is triclinic a = 7.81Å, b = 7.11, c = 6.96, α = 117°12′, β = 93°47′, γ = 93°24′, Z = 4. Indices are α = 2.29, β = 2.31, γ = 2.33.

Winstanleyite, TiTe3O8, is cubic Ia3, a = 10.963Å. Crystals are cubes, sometimes modified by the octahedron; colour Chinese yellow, H = 4, nD = 2.34.

All of the above species were found in small amounts on the waste dumps of the Grand Central mine, Tombstone, Arizona, associated with a wealth of other tellurites and tellurates.

A new mineral species, vigezzite (Ca,Ce) (Nb,Ta,Ti)2O6, was found near Orcesco, Valle Vigezzo, Prov. Novara, Northern Italy. It forms fiat prismatic crystals up to 2–3 mm length of an orange-yellow colour. The crystals are elongated along the a-axis and flattened on (010). Cleavage at right angles to the prism axis is distinct, fracture conchoidal. Vickers hardness VHN = 396 kp/mm2, corresponding to in the Mohs scale. Refraction indices are high: α = 2.14, γ = 2.315 (NaD, 589 µm), birefringence is 0.175. Optic angle 2Vγ is large. Though intensively yellow coloured, the mineral shows no pleochroism. α = c, β = b, γ = a; optic axial plane is parallel to (010).

Vigezzite is orthorhombie with space group Pmnb or P21nb; a = 7.559±0.01, b = 11.028±0.01, c = 5.360± 0.004 Å, Z = 4. The six strongest lines of the X-ray powder pattern are 4.821 (9) (011), 3.784 (8) (200), 3.036 (10) (031), 2.974 (10) (211), 1.7129 (6) (242), 1.6018 (7) (431).

Electron microprobe analyses lead to the empirical formula (Ca0.82Ce0.24)Σ1.06(Nb0.9Ta0.62Ti0.5)Σ2.02O6. The mineral is not completely homogenous, the ratio Nb/(Nb+Ta) varies from 0.55–0.62. Rynersonite Ca (Ta,Nb)2O6, may represent the Ta-dominant equivalent of vigezzite. Vigezzite occurs together with several other Nb-minerals such as pyrochlore, columbite and fersmite, whose crystallographical and chemical data are reported, in an albitic rock of presumably pegmatitic origin.

Drugmanite occurs as rare colourless transparent platy crystals, up to 0.2 mm, aggregated in bunches, in vugs of a mineralized and silicified limestone. Hardness < 6. Crystals monoclinic, forms {001} {110}, parameters from indexed X-ray powder pattern (and monocrystal measurements): a = 11.110 (11.111) Å, b = 7.976 (7.986), c = 4.644 (4.643), β = 90°18′ (90°.41°). Space group P21/a with Z = 2 giving Dcalc = 5.55. Strongest lines are 4.63 Å (9), 3.752 (IO), 3.350 (8), 3.247 (8), 2.912 (9). Mean refractive index 1.88 from reflectance measurements. Strong dispersion r < v, optic axial plane // (olo), 2Vα = 33±2°. Electron microprobe analysis gave P 8.89, Al 0.85, Fe 6.19, Pb 59.76%, leading to Pb4.02 ( Al0.45)P4.00O17.02·3H2O or Pb2(Al0.22) (PO4)2 (OH)·H2O. Associated minerals are pyromorphite, anglesite, corkite and phosphosiderite. Named for J. Drugman, Belgian mineralogist (1875–1950).

Tomichite, (V,Fe)4Ti3AsO13(OH), a new mineral species related to derbylite, has been found in the ‘green leader’ gold lodes at Kalgoorlie, Western Australia. It is monoclinic, with space group P21/m or P21; a = 7.119 (3), b = 14.176 (5), c = 4.992 (2) Å, β = 105.05 (I)°, Z = 2. Strongest diffraction lines: 3.092 (4), 2.836 (9), 2.663 (10), 1.572 (5). Tomichite occurs as tiny euhedral crystals in quartz; associated minerals are vanadian muscovite, rutile, pyrite, and calaverite. Tomichite is black, has a black streak, lacks internal reflections, is moderately anisotropic, and has S.G. = 4.16 (meas.), 4.42 (calc.). Reflectivity values are 470 nm-15.9%, 546 nm-16.3%, 589 nm 16.6%. Microhardness is VHN 800, using 50 g load.

Late-stage acid pegmatites veining the predominantly ultrabasic Currywongaun-Doughruagh intrusion are frequently associated with amphibole-rich reaction borders in the adjacent wall-rocks. The chemical and mineralogical changes resulting from reaction between an acid pegmatite vein and the orthopyroxenite wall-rock are assessed from chemical analyses of rocks and microprobe analyses of the amphiboles forming the zoned reaction border. The main chemical change was the addition of H2O to the wall-rock; otherwise the formation of the anthophyllite and hornblende of the reaction border from pyroxene was virtually isochemical. Enrichment in other chemical species, notably Ca and AI, was restricted to the region close to the interface between the reactants. This inhibited style of reaction is attributed to the initial marginal crystallization of the acid pegmatite melt acting as a barrier to subsequent metasomatic interchange.

Intrusion of the Bee Mountain soda microsyenite plug in southwestern Brewster County, Texas established conditions of low grade contact metamorphism in the upper Cretaceous Boquillas and Pen Formation sedimentary rocks. It is unlikely that load pressure exceeded 330 bars or that temperatures exceeded 470 °C at the intrusive contact. Thermally unaltered parent materials predominantly contain ortho- and allochemical low-magnesium calcite, silt-sized quartz, calcium montmorillonite, kaolinite, and volcanic glass. Incipient metamorphism is marked by the appearance of xanthophyllite followed by prehnite formed at the expense of xanthophyllite and montmorillonite. Near the soda microsyenite contact prehnite has decomposed to yield grossular and epidote group minerals, and apophyllite has replaced calcite where fluorine-bearing solutions have reacted with the parent material. Textural modifications include the recrystallization of calcite, redistribution of some of the mineral phases, and decreased friability in the marly layers.

Ejecta associated with the Xalapasco de la Joya maar 33 km northeast of San Luis Potosi, SLP, Mexico, contain a diverse assemblage of nodules of postulated lower-crust/upper-mantle origin. Spinel lherzolites constitute the most abundant group of nodules and display chemical evidence that crystallization or equilibration took place at temperatures and pressures consistent with upper mantle genesis. Estimated equilibration temperatures and pressures range from 825 to 1025 °C and 7 to 19 kb.

The field relationships, petrography and mineralogy, including probe analyses of olivines, pyroxenes, and plagioclases, of the Karroo dolerite dike swarm of southern Malawi, are described. Rock analyses are given and define a typical tholeiitic trend of iron enrichment. The most magnesian rocks are thought to represent fairly picritic liquids. A number of authors have shown that there are significant geochemical differences between the basaltic rocks of the northern and southern parts of the Karroo outcrop in southern Africa, notably for elements such as Al, P, K, Ti, and Ba. The Malawi data presented here, however, show trends that are the reverse of those found hitherto, the Malawi dolerites being closely comparable with the rocks of the central Karroo basin of South Africa and Basutoland. The striking regional variation in the geochemistry of the Karroo basaltic rocks over southern Africa is independent of the tectonics or position vis-à-vis the central Karroo basin, and so probably reflects mantle heterogeneity.

Microprobe analyses of relict pyroxenes in meta-basalts from thrust slices of the Peel fault zone, Glenrock Station, NSW, demonstrate that the majority of these rocks have a tholeiitic affinity. Those of Ordovician to L. Devonian(?) age in the upper thrust slices show a greater Fe-enrichment, and lower wollastonite, Al and Ti contents than their Devonian counterparts in the lowest thrust sheet. The pyroxene data also indicate that some rocks are geochemically transitional between tholeiitic and alkaline magmas. The relict pyroxenes in metadolerites emplaced in the Devonian sequence show that these rocks are transitional to tholeiitic in character and that they appear not to be consanguineous with the metabasalts.

Wolfeite (Fe,Mn)2PO4(OH) and barbosalite FeIIFeIII2(PO4)2(OH)2 are the principal phases in phosphate pods from the core of a zoned altered granitic pegmatite at Thackaringa. Chemical analyses of the wolfeite show it to be Fe-rich and extends the triploiditewolfeite isomorphous series (Frondel, 1949) from ΣFe/Mn = 3·39 (this study) to greater than 100 (Clark and Couper, 1979).

The results of measurements of diffuse reflectance over the wavelength range 200 < λ < 2500 nm are reported for sphalerite, cinnabar, alabandite, chalcopyrite, bornite, orpiment, stibnite, bismuthinite, enargite, and pyrargyrite, and for eight pyrite-type and four NiAs-type compounds. Some spectral assignments have been made.

Optical properties are related to the absorption spectrum (and through this to composition and structure) in a rational way. Absolute reflectances tend to increase with mean atomic number (z) through the operation of the ‘z-sum rule’, and at constant z they decrease as the band gap increases. Bireflectance is structurally controlled, being weak in derivatives of the cubic sphalerite and pyrite structures, moderate in derivatives of wurtzite and NiAs, and strong in anisodesmic structures such as that of stibnite. Extreme bireflectance occurs in anisodesmic structures with strong dichroic absorption bands in the visible (molybdenite, covelline).

The dispersion of reflectance (dR/dλ) depends on the position of the centre of the main absorption envelope in relation to the visible spectrum. For λ > , dispersion is normal (Rblue > Rred, dR/dλ negative), the streak is light or coloured, and polished surfaces tend to be bluish. For λ < , dispersion is reversed (Rred > Rblue), the streak is dark, and polished surfaces are yellowish. Polished surfaces are white or grey if absorption varies little through the visible or strongly coloured if it varies rapidly (covelline, chalcopyrite).

Chrome spinels from seams in the Rhum layered intrusion, Inner Hebrides, generally contain very fine platelets of exsolved phases. Despite the low bulk Ti content (< 1%) of the spinel grains, analytical electron microscopy shows these platelets to be highly enriched in titanium. Electron diffraction indicates the presence of platelets of two different phases, one a magnesian ilmenite, the other a defect spinel intermediate phase. The platelets are the result of oxidation of the spinel at moderate (c. 600 °C) temperatures and their distribution suggests that oxygen fugacity gradients existed across some of the seams.

This study is devoted to fractures produced by natural and artificial shock processes in non-porous rocks consisting essentially of quartz and feldspar. Petrological and textural investigations were performed using optical and scanning electron microscopic techniques. A microfracturation index is adapted from Short (1966, 1968a, b) in order to compare the fracture densities in different materials shocked in different ways. In all cases, the density of fractures in quartz and feldspar increases with increasing pressure to about 200 kb. At higher pressure this trend is reversed. Fracturing is more intense in feldspar than in quartz. Plane shock waves produced in laboratory scale experiments induce more fracturing than natural shock waves. However, such an increase is no larger than the scatter among the data and the experimental technique used in the laboratory can be considered realistic in terms of fracturing. Finally the correlation between pressure and fracture density is too poor to be of use for quantitative pressure calibrations of naturally shocked materials.

There is no direct correlation between the density of fractures and the number of planar elements observed. There is a negative correlation between fracturing and formation of diaplectic glass, Diaplectic glasses are remarkably weakly fractured compared with shocked minerals. The abrupt change in the slope of the curve giving the dependency of the density of fractures with pressure corresponds to the pressure at which diaplectic glass is formed. From petrographic considerations it is deduced that fracturing occurs at the end of the shock sequence, on pressure release, while diaplectic glasses are forming or already formed. Hypotheses of mechanical and thermal fracturing are examined; both are plausible, but a thermal origin may be preferred. The mechanism of formation of diaplectic glass is discussed with respect to results and deductions obtained by the study of fracturing. Diaplectic glass could represent a decompressed highdensity glass resulting from a single state transformation of a mineral, at high pressure.

Transmission electron microscopy of several chondritic meteorites reveals exsolution products of two kinds in olivine. The coarser variety comprises particles that have nucleated heterogeneously on subgrain boundaries. Electron microprobe data confirm that these are chromite. The second variety, consisting of smaller precipitates distributed randomly, is interpreted as a homogeneously nucleated analogue of the first. It is potentially important as an indicator of cooling history. The aluminium-poor compositions of heterogeneously exsolved chromites suggest that some Cr may have entered tetrahedral sites in olivine during initial rapid crystallization from the melt.

Free energies of formation of divalent metal ion zippeïtes, M2(UO2)6(SO4)3(OH)10 ·nH2O, M = Mg,Co,Ni,Zn have been determined from solution studies and metal speciation calculations, in water. It is found that in the compounds, the number of molecules of water of crystallization is equal to 8. This is at variance with a previous report (Frondel et al., 1976), but it has been found that some at least of the water content of zippeite is either nonessential or very loosely bound in the structure. Based on the octahydrate formulation, values are −3506, −12695, −12683 and −12870±4 kJ mol−1 for the Mg,Co,Ni and Zn end-members, respectively. Almost all of the differences in the values are accounted for by those values for the metal ions alone with the exception of Znzippeïte where a discrepancy of some 22 kJ mol−1 is found. Even this value is small however, and the chemical studies indicate that extensive mutual solid solution between all end members is to be expected. These findings agree perfectly with observations on the composition of naturally occurring zippeite minerals of this group.