Found at a small prospect in the Artillery Peaks area, Arizona. Luddcnite occurs in oxidized Cu-Zn ores with fluorite, alamosite, and cerussite. Colour nickel green, H = 4, G meas. 4.45.

Strongest X-ray lines are 7.361(10), 3.173(10), 2.918(8), 5.218(7), 4.226(5), 3.411(5), 2.888(5), 3.650(4). A possible cell found by Ito method is a = 7.85, b = 20.06, c = 14.72 Å, β = 90.78° (monoclinic). Optically (+), α = 1.852, γ = 1.867.

Chemical analysis by wet methods gave CuO 13.2%, PbO 35.1, SiO2 25.7, H2O 20.5, TiO2 (leucoxene impurity) 4.7. Not all water need be essential, hence Cu2Pb2Si5 O14·nH2O. The new mineral and name have been approved in advance of publication by the Commission on New Minerals and New Mineral Names, IMA.

Barium feldspar and barian muscovite are major constituents of the Aberfeldy Ba-Zn mineralization. Celsian varies from equigranular to a platy habit in quartz-celsian rock and forms porphyroblasts in schist and marble. Hyalophane is less common. Barian muscovite is a major component of the schist in the mineralized zone. Celsian (> 80 % Cn) and/or hyalophane coexist with muscovite containing c.6% Ba, and c.8.5% Ba was measured in muscovite from one feldspar-free specimen. Cymrite separated from foliated quartz-celsian rock conformed to the formula BaAl2Si2O8·H2O. The rock textures reflect regional metamorphism, but it is believed that the barium silicates are ultimately authigenic in origin. The platy habit of much of the celsian may have been inherited from cymrite formed during the development of tectonic fabrics.

The new method proposed by Ferguson (1980, 1981) for estimating the T-site occupancies in K-rich feldspars from lattice constants is discussed and compared with the linear model using the structural indicators Δ(bc), Δ(b*c*), Δ(αγ), Δ(α*γ*). The latter method appears to be considerably more effective in view of its wider application to alkali feldspars of different compositions and structural states. Ferguson's (1980, 1981) method has been conceived for K-rich feldspars alone and may produce results that tend to be more erroneous the further a K-rich feldspar lies from the two-step ordering paths involved in the formulation of the determinative procedure itself.

The perthite megacrysts from charnockitic and non-charnockitic members of a sialic intrusive complex in the Varberg area of south-west Sweden have been investigated by powder X-ray diffraction. The extent of Al/Si order in the K-feldspar host lattices of the megacrysts is restricted in all but the major alkali granite differentiate. A direct relationship between the hydration state of the containing rock and the degree of order of the megacryst lattices is indicated. High lattice strain is common to all the megacrysts but decreases progressively with increasing triclinicity.

Although a ‘chlorite’ is usually simple to recognize in thin section because of its characteristic colour, form, and often very low or anomalous interference colours, the identification of the various species is more difficult and requires both chemical and X-ray work for accurate determination. Roy and others have demonstrated that chlorites are polymorphous and occur in two structural groups, the normal 14 Å chlorites and the 7Å septechlorites (Nelson and Roy, 1958). Many chlorite varieties may be found in both structural states, low-temperature end-members and compositionally extreme end-members favouring the septechlorite structure, especially antigorite, amesite, chamosite, greenalite, and cronstedtite. Phillips (1964) subsequently proposed that six variables, Y, R3+, R2+ , Σ, H, plus the appropriate structural designation, must be fixed to define completely a variety of the chlorite group and from this he developed a numerical system of classification. Unfortunately these specific chemical and structural properties cannot be directly recognized by normal optical methods.

A chalky white, fibrous mineral, in the amygdales of Tertiary basalts from the Gobbins area, Co. Antrim, has been discovered to be a new mineral. It consists of fibrous dusters of lath-shaped crystals showing straight extinction with negative elongation. Its refractive index is ɛ 1.489, ω 1.494 (both ± 0.003) and specific gravity is 2.194 (meas.), 2.147 (calc.). The mineral is tetragonal with ɛ = c (elongation); a = 10.145, c = 9.788 Å. The strongest powder lines (in Å, intensity in brackets) are: 7.10, 4.10, 3.19(100); 3.10, 2.69(80); 5.07(50); 2.64(40). A spectrographic analysis shows major Si, Al, minor Ca, Na, Cu, and trace Fe. Two chemical and one probe analysis give the ideal formula Na4(Ca,Mg,K2)Al6Si10 O32.12H2O. The name gobbinsite (approved by the IMA Commission on New Mineral Names) is suggested after the locality. The type specimen (I7881) is preserved in the Ulster Museum.

Rotation and Weissenberg photographs of gobbinsite and garronite show doubled reflections, which are explained on the basis of submicroscopic twinning on (101). Relationship between gobbinsite and garronite is discussed and evidence is presented for the occurrence of minute amounts of a merlinoite-type mineral that forms regular intergrowths with gobbinsite and garronite.

Mesoperthite feldspars from hypersolvus granites, with granulite-facies mineralogy from the Scourian complex, N.W. Scotland have an average bulk composition of (Ab0.58Or0.42)88An12. The mesoperthites have an Ab/Or ratio close to the critical composition of the alkali feldspar solvus for anorthite-free compositions. The critical temperature of the ternary feldspar solvus is estimated at high anorthite contents and used to indicate a temperature in excess of 1000°C for the crystallization of the granite sheets prior to granulite-facies metamorphism and permits a maximum water content in the melt of 1%.

Manganese nodules from the central Pacific contain poorly crystalline todorokite and also small amounts of a post-depositional recrystallization todorokite. The Cu and Ni of the nodules is preferentially concentrated in the latter. Crystalline todorokite on Groote Eylandt does not contain Cu or Ni, providing further evidence that these elements are not necessary to the development of well-crystalline todorokite.

Sections perpendicular to [001] of ion-thinned specimens of amosite (fibrous grunerite) from Penge, Transvaal and anthophyllite from Paakila, Finland and Söndeled, Norway, have been examined by high-resolution transmission electron microscopy. Observations on the nature of grain boundaries and alteration are compared with those of other workers on other fibrous amphiboles. Fibrous crystals grow with their fibre (c) axes approximately parallel to one another but they have considerable rotational disorder about that axis. Grain boundaries are generally irregular in shape and only follow low-index planes for short sections. In all specimens the amphibole has undergone some alteration to sheet silicates along grain boundaries, fractures, cleavages, and multiple-chain lamellae. Anthophyllite alteration products are talc, serpentine and chlorite, and amosite alteration products approximate to iron analogues of talc and serpentine. Talc layers are generally planar and their orientation is strongly controlled by the amphibole structure, whereas serpentine and chlorite layers often curve and their orientations are less frequently related to that of the amphibole. Comparison of specimens which appear finely fibrous in hand specimen with those which appear coarser, acicular or massive suggests that the nature of fibres produced by crushing is mainly controlled by the grain boundaries in the former type, but other factors such as fractures, cleavages, and defects are more important for the latter types.

Two palladium arsenide-antimonides have been found as small inclusions associated with native gold at Hope's Nose. One of the minerals has been identified as isomertieite; the other is chemically very similar to mertieite-II (Cabri et al., 1975). Electron probe microanalysis gives the formula of the isomertieite as (Pd10.89 Au0.08Cu0.03)Σ11.00(Sb2.01As1.99)Σ4.00 and of mertieite II as (Pd7.90Au0.07Cu0.01)Σ7.98(Sb2.43As0.59)Σ3.02. The relectance spectra of isomertieite in air and in oil at intervals of 10 nm from 400–700 nm are tabulated. The luminance values of the Hope's Nose isomertieite are 55.5 % in air and 42.5% in oil. The type specimen of isomertieite from Itabira, Minas Gerais, Brazil, has been re-examined; a new electron probe analysis is given and improved reflectance spectra are tabulated. The latter gives luminance values of 54.3% in air and 41.3% in oil.

Favourability of uranium mineralization in six tertiary granitic plutons of the Alaska Range in the Talkeetna and Mt McKinley quadrangles was studied. The uranium concentrations of drainage sediment samples, which were collected and analysed by the Los Alamos Scientific Laboratory for the National Uranium Resources Evaluation, were statistically evaluated and compared to those of the surrounding area using factor and cluster analyses. The results of this study suggest that five of the six plutons under consideration are likely to contain uranium mineralization. These plutons are probably a potential source rock for uranium in the region.

The new minerals were found together in oxidized ores at the Bambolla mine, Moctezuma, Sonora. Both occur with various iron oxides, emmonsite, schmitterite, and kuranakhite. Cuzticite, Fe2TeO6 · 3H2O, is yellowish, H = 3, G = 3.9, occurring as crusts with a scaly structure. No single crystals were found, but X-ray powder data indicate a hexagonal cell a = 5.045, c = 14.63 Å. Strongest lines are 3.256 (10), 2.518 (7), 4.871 (4), 2.239 (3), and 1.564 (3).

Eztlite, Fe6Pb2(TeO3)3TeO6(OH)10 · nH2O, is blood red, as paper-thin sparkling crusts, H = 3, G = 4.5. A possible cell found by the Ito method is monoclinic a = 6.58, b = 9.68, c = 20.52Å, β = 90° 15′; strongest lines are 3.426 (10), 3.289 (10), 4.037 (9), 3.239 (9), and 2.445 (7B).

Both minerals and their names have been approved by the Commission on New Minerals and Mineral Names, IMA.

Pitticite is re-examined analytically and found to be a gel-like mineral of widely varying composition. Previously reported minor amounts of accessory elements are indeed present in pitticite. The name pitticite has validity only as a generic name for gel-like ferric iron arsenate minerals of varying composition.

Yukonite is reported from the Sterling Hill mine, Ogdensburg, New Jersey, the second occurrence. New data for yukonite suggest the name should be retained.

The Vulsinian district is the largest and northernmost of the Roman Provinces. There is very little modern mineralogical data on the Italian Pliocene to Recent perpotassic alkaline volcanic rocks and this account deals with the compositions of the phenocrysts in the Vulsinian lavas.

The lavas comprise two suites: a leueite-bearing undersaturated series of leucitites, leueite tephrites, leucite phonolites, and trachytes; and a subordinate hy-normative series of mainly trachytes and latites. All lavas are porphyritic with mostly 1–15 vol. % phenoerysts. No cumulates were found. Major elements, and Cr and Ni were determined in the phenocrysts by microprobe analysis and more than 20 trace elements were determined on mineral separates by PIXE.

The undersaturated suite. Ubiquitous clinopyroxene phenoerysts belong to the Di-Hedss series and range from Di97 to Di46. Important amounts of Fe3+ are always present. In the mafic rocks the diopside is chromian, but Ti is low. AI mainly substitutes in the Z positions in all lavas. Only minor Na enrichment occurs with increasing total Fe (0–7 mole % acmite) and thus Ca ferri-Tschermak's component is important. In many of the maric lavas diopside mantles green cores of salite, which has a composition very like the salite of felsic lavas. Leucites contain 5–22 mole % orthoelase in solid solution, but show no systematic variation. Plagioclase, mostly An93-An72, occurs in the felsie lavas, and alkali feldspar only in some phonolites. They both have exceptionally high concentrations of Sr and Ba, with a maximum of 1.3 wt. % SrO and 5.6 wt. % BaO in hyalophanes. Olivine, Fo92-Fo66, occurs in some leucititic lavas in mostly accessory amounts. Phlognpite, magnetite and nepheline are accessory phases of the felsic lavas. Apatite only occur as micro-phenocrysts of the fclsic lavas. Haüyne in trace amounts is found in a few phonolites. Pargasitic amphibole microphenocrysts are found in one lava.

In most marie members diopside ±leuctie ±olivine were liquidus phases. This study does not confirm that these rocks are related by crystal fractionation. In more felsie lavas clinopyroxene (salite-ferrosalite) and leucite are joined by: plagioclase, magnetite ±phlogopite, and Ba-rich alkali feldspar ±haüyne. The felsic rocks are thought to be related by crystal fractionation.

Salitic green cores of phenocrystic pyroxene, mantled by diopside in rocks which also carry normally-zoned diopside, are relicts which provide evidence of either a relatively high PH2O, prior to the crystallization of diopside or magma mixing in the earlier life of these lavas. Pyroxene chemistry points towards low-pressure crystallization (2 kbar), generally in a dry environment.

The hy-normative suite. All lavas have phenocrysts of augite, sanidine, plagioclase, magnetite, biotite, and olivine. The pyroxene is less calcic and has less alumina, but is otherwise rather similar to the salites of the undersaturated suite. Compared to the undersaturated suite, feldspars do not have high Sr and Ba, magnetite has higher TiO2 and olivine crystallized from even the felsic lavas. The pyroxenes show the signs of low-pressure crystallization.

A new occurrence of awaruite, from India, is reported in the ultramafic units of the Dras area which form part of the Indus Suture ophiolites in Kashmir Himalaya. Its formation in these rocks suggests a low-temperature process of serpentinization. Ni and Fe released from olivine and/or pyroxene must have formed awaruite peragenetically next to magnetite and pentlandite.

Basement rocks of Santorini have been locally impregnated by iron oxides and other minerals. The hydrothermal fluids which caused the mineralization have extensively altered the impregnated rocks, but left granditic garnets in these unaffected.

Mössbauer spectroscopy and differential X-ray diffraction show that the iron oxides present are goethite and hematite in a ratio of about 2 : 1. The presence of hematite indicates that these minerals formed, directly from a hydrothermal phase, at higher temperatures than the recent submarine iron oxide deposits of Santorini, which contain no hematite.

Nucleation and crystal growth of plagioclase have been studied in two basaltic melts by one atmosphere, constant-rate and variable-rate cooling experiments using the wire-loop technique (Donaldson et al., 1975). Constant-rate cooling studies indicate that the length of the incubation period prior to nucleation varies systematically with the degree of supercooling and with the cooling rate. Attempts to determine the rates at which the marginal parts of two dykes (from the Isle of Arran, SW Scotland) cooled, by the attempted reproduction of the natural textural features, in constant-rate cooling experiments suggest that for one of the dykes, plagioclase phenocrysts at the contact could have grown at a cooling rate of approximately 3°C/hour and the groundmass plagioclase laths at faster cooling rates in excess of 10°C/hour. For the other dyke the plagioclase laths in the rocks 0.5 cm from the dyke contact probably grew at rates slower than 2°C/hour. Attempts to validate experimentally the Jaeger (1957) cooling model for the two dykes suggest that the dykes cooled at much slower rates than the theory predicts.

By constructing ball-and-spoke models an attempt has been made to arrive at the atomic arrangements on the twin boundaries of four twins of calcite and one of aragonite. The Miller indices of the twins of calcite are (111), (110), (100) and (11). The twin plane in aragonite is (110). Each of the models of calcite twins has the same plane for twin plane and composition plane, and in each case it is a true mirror plane. Aragonite has a pseudo glide plane parallel to (110) gliding in the [001] direction. By making this pseudo symmetry element into a true glide plane a good model of the twin is obtained. In the (111), (110) and (100) twins of calcite all the CO3 groups in the composition plane are parallel to it. In the (11) twin the composition plane contains only CO3 groups and these are perpendicular to it.

The Alderley Edge deposit, Cheshire, England has been mined principally for Cu and Pb. Here, veins and disseminations occur in coarse-grained clastic sediments of Triassic age and are classified as belonging to the red-bed type of mineralization.

Examination of material in polished and thin section has shown the mineralization to be multiphase. The earliest opaque phases are associated with the diagenesis of the sandstones and include authigenic anatase, plus bravoite, pyrite, and chalcopyrite within authigenic quartz overgrowths. This stage of mineralization was followed by the formation of intergrown bravoite, pyrite, chalcopyrite, sphalerite, and galena accompanied by minor amounts of Ni-Co-Fe sulpharsenides, marcasite, and tetrahedrite cementing the clastic grains. This primary assemblage has undergone extensive alteration resulting in the formation of djurleite, covelline, and blaubleibender covelline accompanied by Pb and Zn carbonates and sulphates. Later, extensive shattering of the cemented clastic grains has been infilled by supergene Cu, Pb, and Zn carbonates and sulphates, limonite, and other secondary minerals.

Electron probe microanalysis of the sulphides shows the pyrite to contain significant Ni and Cu but lesser amounts of Co; the sphalerite to be an Fe-poor variety but to contain Cd, and the chalcopyrite to contain Sb. Ag is present in appreciable amounts in tetrahedrite and occurs in trace amounts in both sphalerite and chalcopyrite but not in galena. The concentration of Ag increases with the alteration of the primary sulphides to secondary sulphides. This is most clearly demonstrated by the alteration of chalcopyrite to an idaite-like phase and finally to djurleite when the Ag content increases from 0.10 to 2.35 wt. %.

The petrographical and chemical characteristics of the tourmalinite pebbles from the Lower Devonian conglomerates of Belgium are presented together with selected trace element data. The tourmalinites are shown to represent metasomatically altered rocks of variable origin and composition. A model of subvolcanic hydrothermal alteration is proposed.