bluuebunny/crossref_metadata_2025 huggingface dataset:
Emeleusite: a new LiNaFeIII silicate from south Greenland
Authors: Upton B. G. J. , Hill P. G. , Johnsen O. , Petersen O. V.
Published: December 2006

Emeleusite (Li2Na4Fe2IIISi12O30) is an orthorhombic (pseudohexagonal) mineral occurring as euhedra within a facies of a peralkaline trachyte dyke. The composition is: SiO2 70·75; TiO2 0·55; ZrO2 0·10; Al2O3 1·34; Fe2O3 12·13; MgO 0·10; MnO 0·03; Na2O 11·98; Li2O 2·78:99·76. The density is 2·775 g/cm3 (calculated) and 2·76(7) g/cm3 (determined); hardness 5–6. It is colourless, transparent, and has a glassy lustre. Emeleusite is biaxial negative with 2Va, varying from near-zero to c. 30° r » v. The refractive indices are α 1·596; β 1·597; y 1·597; with α ∥ b; β ∥ a; y ∥ c. Emeleusite can occur as interpenetration triplets with {110} as twin planes. The space group is Acam or Aba2 with a = 10·073±0·002 Å; b = 17·350±0·005 Å and c = 14·010±0·005 Å. Z = 4. Prominent powder diffraction lines are 7·001(5) 002, 4·352(10) 220, 040, 3·501(7) 004, 3·209(8) 311, and 3·090(7) 124. While the structure is as yet unknown it is suggested that it is an orthorhombic associate of the milarite group.
Partition coefficients of alkali and alkaline-earth elements between alkali feldspar phenocrysts and their lava matrix
Authors: De Pieri Renzo , Quareni Sergio
Published: December 2006

Plots of partition coefficients (mineral/ matrix) against ionic radius of the alkali and alkaline earth elements in forty-four alkali feldspars from rhyolites and trachytes show two kinds of diagram, one for homogeneous alkali feldspars with a single peak, and the other for cryptoperthites with a wide spread of points, which cannot represent a single peak, but may probably be explicable in terms of two peaks. The difference in behaviour does not seem to be due to the chemical composition, but is apparently related to the crystallo-graphic features of the alkali feldspar structures. In particular the presence of two peaks in the diagrams of the cryptoperthites seems to be due to the existence of lattice positions suited to receive bigger ions (K, Ba, Rb) and smaller ions (Na, Ca, Sr) in the potassic and sodic domains.
Deweylites, mixtures of poorly crystalline hydrous serpentine and talc-like minerals
Authors: Bish David L. , Brindley G. W.
Published: December 2006

An X-ray and chemical examination of deweylites reveals that they are intimate mixtures of very poorly ordered trioctahedral 2:1 and 1:1 layer silicates. The 2:1 mineral exhibits no swelling in the presence of ethylene glycol or water and is best described as an extremely fine-grained and highly disordered form of talc, for which the term kerolite is often used. Stevensite is not a component of deweylites. The 1:1 component most closely resembles a disordered chrysotile.

Evaluation of the chemical data, including values for H2O +, shows that both end-members are hydrated to various degrees. This hydration is most probably attributable to the presence of water molecules and hydroxyls associated with the large surface areas and unbalanced surface bonds. Formulae for the end-members are approximately R3Si4O10(OH)2·0·3 0·7 H2O and R3Si2O3(OH)4·0·3–0·7 H2O where R is principally Mg, but samples with more or less H2O are entirely possible due to variations in crystallinity. No specific formula can be given to deweylites as they are mixtures with variable proportions of the components. The name is useful, however, as a field or ‘box’ term, similar to the use of garnierite and limonite.
Titaniferous clinohumite from Gardiner Plateau Complex, East Greenland
Authors: Nielsen T. F. D. , Johnsen O.
Published: December 2006

Titaniferous clinohumite occurs as a major constituent in the centres of late magmatic veins in the Tertiary ultramafic, strongly alkaline Gardiner Plateau Complex in East Greenland (69° N. and 32° W.). The complex is briefly described and an electron microprobe analysis of titaniferous clinohumite is presented. This gives the following: 38·44% SiO2, 2·99% TiO2, 4·87% FeO, 51·89% MgO, 1·3% F, H2Ocalc 1·50%, and total 100·44%. Optical data, density, and unit cell dimensions are also presented. Of magmatic occurrences, titaniferous clinohumite has otherwise only been reported in certain kimberlites and carbonatites.
Quantitative determination of analcime in pumice samples by X-ray diffraction
Authors: Parker R. J.
Published: December 2006

A quantitative X-ray diffraction method has been successfully applied to the determination of analcime in pumice rock samples. A calibration line was constructed from spiked pumice standards (range: 0 to 42%) and the mean relative error of the standards on the calibration line was < 0·6%. The major-element compositions of the samples and standards were available, and this allowed the total mass absorption coefficients to be calculated. The latter were then used to correct the sample and standard intensities for absorption effects resulting from compositional variations. When compositional data already exist, the calculation of the total absorption coefficient provides a rapid and accurate alternative to direct measurement, or to the use of an internal standard.
The unit cell of talc
Authors: Akizuki M. , Zussman J.
Published: December 2006

Six specimens of talc studied by the electron microscope lattice-imaging and diffraction techniques were found to have the triclinic one-layer (1 Tr) structure. Since no evidence of a monoclinic two-layered structure was found in any specimen it is concluded that the 1 Tr structure is the common one for talc, and it may, moreover, be the only one. Extremely fine polysynthetic twinning and single intrinsic stacking faults were found in talc.
Kidwellite, NaFe93+(OH)10(PO4)6·5H2O, a new species
Authors: Moore Paul B. , Ito Jun
Published: December 2006

Kidwellite, NaFe93+(OH)10(PO4)6·5H2O, monoclinic, Z = 2, a = 20·61(7) Å, b = 5·15(1) Å, c = 13·75(6) Å, β = 112·64(15)·, space group A2/m, Am, or A2, is a new species that occurs in moderate abundance as a late-stage mineral associated with rockbridgeite, dufrenite, beraunite, and strengite in novaculite deposits. Colour lively pale chartreuse-green, to greenish-yellow, greenish-white, and bright yellow. H = 3, lustre silky, streak yellow, cleavage {100} perfect, habit acicular elongated parallel to [010], flattened on {100}, biaxial (−), α = 1·787(5), β = 1·800(5), γ = 1·805(5), 2V large, β∥b, not discernibly pleochroic.

The mineral is moderately widespread as a replacement of rockbridgeite and beraunite from the Ouachita Mountains, Arkansas; Indian Mountain, Alabama; Irish Creek, Virginia; Waldgirmes, West Germany. A related, but apparently distinct, species is also noted from the McMahon pegmatite, South Australia, and the Sapucaia pegmatite, Minas Gerais, Brazil.
Geochemistry of some lateritic nickel-ores with particular reference to the distribution of noble metals
Authors: Ahmad S. , Morris D. F. C.
Published: December 2006

Platinum, palladium, gold, and iridium have been determined by radiochemical neutron-activation analysis in three lateritic profiles developed on serpentinized peridotite. In addition, a number of major, minor, and other trace elements have been estimated by conventional chemical, instrumental neutron-activation, and radiochemical methods. The fractionation of the elements as a result of the tropical weathering has been investigated as a function of depth. Each of the profiles L--Guatemala, BNC--New Caledonia, and BIP--Indonesia- has a lower decomposed serpentinite zone and upper zones enriched in iron nl oxides and hydroxides.
The crystal structure of hohmannite, Fe2(H2O)4[(SO4)2O].4H2O and its relationship to amarantite, Fe2(H2O)4[(SO4)2O].3H2O
Authors: Scordari F.
Published: December 2006

Hohmannite is a hydrated sulphate of ferric iron with the formula Fe2(SO4)2(OH)2.7H2O (Palache, Berman, and Frondel, 1951).

Figs. 1 and 2 illustrate the structure of hohmannite. The first shows a complex chain of Fe(O, H2O)6 octahedra and SO4 tetrahedra, which runs along the c axis; the second visualizes the water molecules and an hypothetical hydrogen-bonds system obtained on the basis of electrostatic and geometrical considerations.
The geochemistry of loveringite, a uranium-rare-earth-bearing accessory phase from the Jimberlana Intrusion of Western Australia
Authors: Campbell I. H. , Kelly P. R.
Published: December 2006

The distribution and geochemistry of loveringite, an accessory Ti, Fe±Cr oxide containing U and rare-earth elements (Ln) from the Jimberlana Intrusion, have been studied. Loveringite is most abundant in bronzite cumulates; it is found in trace amounts in early plagioclase-augite-hypersthene cumulates, but is not found in the olivine cumulates or in the late-stage differentiates. Loveringites from the bronzite cumulates have a high Cr content compared with those from the plagioclase-augite-hypersthene cumulates, suggesting that the mineral is stabilized by the presence of Cr in the intercumulus liquid. The Ln pattern shows a strong depletion trend from La to Eu, a sharp reversal between Eu and Tb and a second depletion pattern from Tb to Lu. This pattern suggests that the Ln are substituting into two sites, one much larger than the other.
Amphibolitic rocks from the Precambrian of Grand Canyon: mineral chemistry and phase petrology
Authors: Clark Malcolm D.
Published: December 2006

The amphibolites and mafic schists that occur in the Precambrian metamorphic rocks of the Grand Canyon are divided into five major groups: anthophyllite and cordierite-anthophyllite rocks, early amphibolites, Granite Park mafic complex, hornblende-beating dykes, and tremolite-bearing dykes. Many types of amphibole occur in these rocks. Microprobe analyses identify gedrite, anthophyllite, cummingtonite, and grunerite, as well as three groups of calcic amphiboles. These last range in composition from colourless tremo-litic or actinolitic amphiboles, through pale-green horn-blende, to strongly pleochroic green-brown hornblende, which contains a significant proportion of the tscherma-kite and pargasite endmembers. Phase relationships between the coexisting amphiboles and other minerals are presented for two regional metamorphic events. Assem-blages containing chlorite, garnet, and hornblende were formed during the first event; from the absence of staurolite, but the presence of almandine garnet and oligoclase-andesine, it is concluded that the metamorphic grade was between the upper greenschist and the lower amphibolite facies. The second period of metamorphism produced rocks of the staurolite and sillimanite zones, within which three main ‘subfacies’ can be distinguished on the basis of phase relationships in the mafic schists.
Major element chemistry of the geothermal sea-water at Reykjanes and Svartsengi, Iceland
Authors: Arnórsson Stefán
Published: December 2006

High-temperature geothermal fields in Iceland represent localized anomalies of hot, altered rock in the uppermost part of the crust, which coincide with points of maximum tectonic/magmatic activity. These points correspond to the intersection of oblique fault swarms to the plate boundaries. Geothermal activity under mid-ocean ridges follows probably similar tectonic/magmatic anomalies.

Due to high permeability sea-water invades the bed-rock of the Reykjanes Peninsula, Iceland, and is overlain by a variably thick lens of dilute ground water of meteoric origin. The variable degree of salinity of geothermal waters in the Reykjanes Peninsula has resulted from different degree of mixing of fresh ground water with the underlying sea-water-ground-water in the downflow zones around the geothermal fields. At Reykjanes the geothermal water represents heated sea-water without any freshwater mixing. The difference in the composition of sea-water or sea-water/fresh water mixtures and the geothermal waters is due to basalt/water interaction at elevated temperatures. The major-element chemistry of the geothermal water represents an equilibrium composition at the relevant aquifer temperatures. The activities of silica, calcium, sulphate, and carbonate are thus limited by the solubilities of quartz, anhydrite, and calcite. Fluoride activity is thought to be controlled by an ionic exchange reaction where it substitutes for hydroxyl groups in phyllosilicates. The ratios of individual cations and hydrogen ion are governed by ionic exchange equilibria with hydrothermal minerals, probably smectite and chlorite. The equilibrium pH for the Reykjanes and Svartsengi geothermal waters is 5·5 and 5·1 respectively. Sea-water will become somewhat acid upon heating to more than about 300 °C and equilibration with basalt, the acidity increasing with temperature.
Normal and anomalous tobermorites
Authors: Mitsuda T. , Taylor H. F. W.
Published: December 2006

Tobermorite minerals vary in some proper lies, notably in whether or not unidimensional lattice shrinkage occurs by about 300 °C to give a 9·3 form; specimens that do this are called normal, and ones that do not, anomalous. Data are compared for thirteen natural tobermorites and the extent to which normal or anomalous character is related to other properties is examined. The most definite correlations found are with chemical composition and morphology. The conditions of formation of normal and anomalous tobermorites are discussed in the light of synthetic evidence.
Sedimentary analcime at Murrurundi, New South Wales, Australia
Authors: Nashar Beryl
Published: December 2006

Sedimentary analcime in a small basin in Cainozoic basalt at Murrurundi, New South Wales, has probably resulted from the reaction of Na-rich water on colloidal nontronite derived from volcanic ash. Based on cell dimension (13.713 Å) and Δ2θ(1·81) determined by Saha's (1959) method it is a Group C low-silica type of Coombs and Whetten (1967).
Platinum-iron alloy sample containers for melting experiments on iron-bearing rocks, minerals, and related systems
Authors: Ford C. E.
Published: December 2006

A method of producing platinum-iron alloy sample containers has been developed that allows experiments to be carried out on iron- and volatile-bearing systems with minimal net exchange of iron between the sample and its container. Preliminary experiments carried out using these containers in the temperature range from 1100 °C to 1250 °C and at pressures up to 10 kb over periods of up to 75 hours produced an average iron loss of 10% to 16% (as FeO) compared with more than 50% FeO loss obtained using pure platinum containers. A more judicious choice of alloy composition would reduce this loss still further.
Pargasite from the Eastern Ghats, Andhra Pradesh, India
Authors: Rao A. T.
Published: December 2006

Synopses

Hornblendes are not common in the charnockites of Kondpalli, but occur as an important constituent in the pyroxene granulites and pyroxenites of Seshadripuram hill. Analyses and optical data for two pargasites are given.
Allanite from the Kondapalli charnockites, Krishna District, Andhra Pradesh, India
Authors: Rao A. T.
Published: December 2006

Synopses

The coarse-grained charnockites of Donabanda hill, Kondapalli, contain metamict allanite. An analysis is given, also optical data for the heated allanite, and the conditions of formation of the rocks are shortly discussed.
I. Whiteite, a new species, and a proposed nomenclature for the jahnsite-whiteite complex series. II. New data on xanthoxenite. III. Salmonsite discredited
Authors: Moore Paul Brian , Ito Jun
Published: December 2006

Whiteite, Ca(Fe,Mn)2+Mg2Al2(OH)2(H2O)8[PO4]4,a14·90(4) Å,b6·98(2) Å,c10·13(2) Å,β113° 07(10)′, Z = 2, space groupP2/a,α1·580(5),β1·585(5),γ1·590(5), 2V 40–50°, specific gravity 2·58, is a new species from the Ilha de Taquaral, Minas Gerais, Brazil. It is the Al3+-analogue of jahnsite. The mineral occurs as up to 5 mm tan crystals flattened on {001}. Twinning by reflection on {001} leads to pseudoorthorhombic development. Rather pure material also occurs from Blow River, Yukon Territory, Canada.

For the general formulaXM(1)M(2)2M(3)2(OH)2(H2O)8[PO4]4, it is proposed that forM(3), Al3+> Fe3+, the established members of the series are whiteite—(CaFe2+Mg) and whiteite—(Mn2+Fe2+Mg); and for Fe3+> Al3+, jahnsite—(CaMn2+Mg), jahnsite—(CaMn2+Fe2+), and possibly jahnsite—(Mn2+Mn2+Mn2+).

Xanthoxenite of Laubmann and Steinmetz (1920) is probably stewartite (in part) on the basis of morphological, optical, physical, and paragenetic evidence. The xanthoxenite of Frondel (1949) is proposed as the species type. It is triclinic,PorP1,a6·70(4) Å,b8·85(4) Å,c6·54(3) Å,α92·1(2)°,β110·2(2)°,γ93·2(2)°, Z = 1 for composition.

Salmonsite,c.from Pala, California, is shown to be an intimate mixture of hureaulite and jahnsite on the basis of calculated and observed powder patterns and on reinterpretation of the original chemical analysis published by Schaller (1912). It is a breakdown product resulting from oxidation of Fe2+in the original hureaulite (‘palaite’) along with further aquation followed by fine-grained recrystallization. The reaction proposed is:
The growth of calcium metasilicate polymorphs from supercooled melts and glasses
Authors: Weston R. M. , Rogers P. S.
Published: December 2006

The morphology of calcium metasilicate produced during the crystallization of glasses and melts of approximately metasilicate composition has been investigated. Both isothermal heat treatments and a dynamic crystal-pulling technique were employed. The crystallization took place by a dendritic or spherulitic mechanism, according to which of the crystal polymorphs is stable under the prevailing conditions. The morphology of the crystals is controlled by the ease with which the anionic groups present in the amorphous phase can be incorporated into the growing crystals. This is reflected in the values of the activation energies of crystal growth found for α-CaSiO3 (160 kJ mol−1) and for β-CaSiO3 (319 to 383 kJ mol−1). The Keith and Padden theory of spherulitic crystallization was verified for the growth of β-CaSiO3 over a range of supercoolings. Time-temperature-transformation diagrams have been constructed from the experimental data.
Black elbaite from Corrego do Urucum, Minas Gerais, Brazil
Authors: Prescott B. E. , Nassau K.
Published: December 2006

Black tourmaline from Corrego do Urucum, Brazil, is an elbaite coloured by iron and manganese with blue, green, and pink regions. Polarized spectra show the absorption bands expected in elbaite (Fe-caused blue and green, and pink, which is probably caused by Mn). The colour distribution in the transverse sections does not conform to the symmetry of tourmaline and changes along the length of the crystals. Two distinct growth stages are indicated, separated by a partial dissolution and followed by another dissolution.
Structural state and composition of alkali feldspars in granites of the St. George pluton, south-western New Brunswick
Authors: Cherry Michael E. , Trembath Lowell T.
Published: December 2006

The variation in the structural state of potassium feldspars from the St. George pluton, New Brunswick, Canada, is discussed. Monoclinic potassium feldspars occur near the eastern end of the pluton whereas the granites at the western end contain triclinic potassium feldspars. Although the bulk compositions of the host rocks are all very near the granite minimum melt composition there is a systematic increase in the degree of ordering for both the triclinic and monoclinic suites of feldspars with the more ordered variants tending to occur within rocks nearest the minimum melt composition. There is more abundant textural evidence for the presence of a late-stage fluid phase in the granites containing the monoclinic potassium feldspars. It is proposed that a slower post-crystallization cooling rate was also a factor in the nucleation of triclinic domains in the potassium feldspars at the western end of the pluton.
Sasaite, a new phosphate mineral from West Driefontein Cave, Transvaal, South Africa
Authors: Martini J.
Published: December 2006

A new mineral, sasaite, occurs as white chalky nodules in the soil of a dolomitic cave and seems to be derived from the action of bat guano on clay minerals. Under the microscope it consists of an agglomeration of plates 10–20 µm on greatest dimension and with a rhombic shape. Its formula is (Al, Fe3+)14(PO411(OH)7SO4·83H2O and it is orthorhombic or quasi-orthorhombic. Preliminary crystallographic data based on an orthorhombic cell are a 21·50, b 30·04, c 92·06 Å, Z10, based on a calculated density of 1·747 (observed 1·75). The optical indices are α 1·465, β 1·473, γ 1·477 all ±0·001, and the principal vibration directions are parallel or quasi-parallel to the crystallographic axis.
Magnetic chromites from Kondapalli, Andhra Pradesh, India
Authors: Rao A. T.
Published: December 2006

Synopses

The Kondapalli region (16° 37′ N. 80° 32′ E.) in the Eastern Ghats, Andhra Pradesh, consists of high-grade granulite facies rocks: charnockites, hypersthene granites, and enderbites are plutonic intrusives into khondalites—garnetiferous sillimanite granites, garnetiferous granites, siltimanite-garnet quartzites, and quartzites. Pyroxene granulites of gabbroic and noritic compositions are distinct basic intrusive bodies, occurring as sills and dykes.

Chromite orthopyroxene nodules are enclosed in serpentinite and carbonate rock, formed from altered peridotite; they are younger than the charnockites and pyroxene granulites and are confined to the cores of south-eastern-plunging overturned isoclinal anticlines. The chromites are massive in coarse-layered pyroxenites and granular in fine-layered rocks; those found at Gangineni are magnetic and are associated with bronzite (En77–85), those from the Binny and Loya mines are non-magnetic and associated with enstatite (En88–95).

Chemical analyses and X-ray powder data are given for five specimens, including both types. The magnetic susceptibility appears to increase with increasing Fe3+. The unit-cell size is negatively correlated with Cr3+, A13+, and Mg2+and positively with Fe2+and Fe3+.
Textural evidence for liquid immiscibility in tholeiites
Authors: Philpotts Anthony R.
Published: December 2006

The residual liquids of many tholeiitic basalts and andesites, on cooling, split into iron-rich and silica-rich fractions, which may quench to brown glassy globules and clear glass respectively. More commonly, however, cooling is sufficiently slow for the iron-rich liquid to crystallize to globular single crystals of pyroxene. Depending on the cooling rate, these crystallized globules range in shape from spheres to elongated globules bounded by crystal faces. The fine grain size of the mesostasis of most tholeiites is partly due to these small crystallized globules. The silica-rich fraction, on the other hand, is more commonly quenched to a glass, and when preserved as globules in the crystallized iron-rich fraction, it may be bounded by negative crystal faces of the surrounding pyroxene. Globules of the iron-rich liquid commonly nucleate on the surface of the plagioclase crystals where they can become trapped, later crystallizing to spherical pyroxene grains that mostly contain a minor opaque phase. In contrast, iron-rich globules that form next to pyroxene grains commonly become attached to these crystals, giving them lobate boundaries. The immiscible silica-rich liquid becomes trapped between these lobes and, with sufficiently slow cooling, results in finger-like quartzo-feldspathic inclusions extending in from the margins of the pyroxene grains. These textures can provide evidence of immiscibility in a wide range of volcanic and hypabyssal rocks, even when no glass is present.
Discordant calc-silicate bodies from the St. Just aureole, Cornwall
Authors: Alderton D. H. M. , Jackson N. J.
Published: December 2006

Several discordant, garnet-bearing bodies are described from the St. Just part of the Land's End granite aureole, Cornwall. It is suggested that these formed by a combination of metasomatic replacement and dilation with concomitant precipitation. Other Ca-Fe aluminosilicates (containing large amounts of Zn, Sn, B, and Be) are also present in the bodies. The chemical, petrographic, and field evidence suggests that the introduced material was transported by hydrothermal fluids. These fluids could well be related to the intrusion of the granite and the earliest phases of ore mineralization. Chemical analyses of garnets, calcic amphiboles and one apatite, epidote, diopside, and axinite are given.
Topotactic replacement of augite by omphacite in a blueschist rock from north-west Turkey
Authors: Carpenter M. A. , Okay A.
Published: December 2006

Partial replacement of original igneous augite crystals by omphacite during blueschist metamorphism of a dolerite from the Mihalliççik area of north-west Turkey has been studied by transmission electron microscopy. The replacement occurred topotactically, apparently by ion exchange with a fluid phase, which left the basic pyroxene structure unchanged. Cation ordering in the omphacite caused a symmetry change from C-face centred to primitive with the formation of fine-scale antiphase domains. Selected-area diffraction provides evidence for P2 and P2/c space groups for the ordered omphacite though the best ordered areas show a tendency towards P2/n (reflections violating the n-glide are very weak) and also contain fine, wavy, disordered precipitates approximately parallel to (too).

It is suggested that the replacement temperature was below the cation-ordering temperature and that the omphacite grew in a metastable, disordered state. Subsequent ordering occurred under irreversible conditions via a series of intermediate structures. The ordering sequence may illustrate the relationship between different ordering schemes in other blueschist pyroxenes.
Aegirine of possible authigenic origin in Middle Devonian sediments in Caithness, Scotland
Authors: Fortey N. J. , Michie U. McL.
Published: December 2006

An occurrence of aegirine in Middle Devonian lacustrine beds in Caithness is described. The mineral occurs as euhedral to subhedral prismatic crystals within a finely laminated siltstone. Microprobe analyses reveal a remarkably ‘pure’ composition consisting almost entirely of Na, Fe3+, Si, and O. X-ray diffractometry yielded the unit cell data: a 9·657 Å, b 8·800 Å, c 5·296 Å, and β 107·37°. Comparison with other natural aegirine compositions shows marked differences from those of igneous or metamorphic origin but a close similarity to a unique occurrence of authigenic aegirine in the lacustrine Green River Formation of Wyoming, U.S.A. Consideration of the nature of the Caithness occurrence, and comparison of the Devonian Orcadian basin with the Eocene Green River basin indicate similar geological environments. It is suggested that the mineral formed in hypersaline conditions in which sodium may have been derived from contemporaneous alkaline volcanism within the Orcadian basin.
Study of the sector structure in adularia by means of optical microscopy, infra-red absorption, and electron microscopy
Authors: Akizuki Mizuhiko , Sunagawa Ichiro
Published: December 2006

Surface microtopography of habit faces, and internal textures of corresponding growth sectors of adularia from the Rhonegletscher, Switzerland, and the Seikoshi mine, Japan, were studied by means of optical polarizing microscopy, reflection interference contrast, electron microscopy, and infra-red absorption spectroscopy. Thin sections parallel to the growth plane were prepared from the specimen whose as-grown face was pasted on a glass slide. Most internal textures seen optically in the thin sections correlated well with the growth patterns for both specimens (fig. 1). Thin foils prepared by ion-thinning from the Rhonegletscher adularia show, under the electron microscope, coexisting heavily cross-hatched areas giving diffuse diffraction spots and homogeneous areas giving sharp diffraction spots. As a whole, adularia from the Seikoshi mine gives more homogeneous and much weaker cross-hatching than the Rhonegletscher specimens. Also, infra-red absorption spectra, which correlate very well with the Al/Si ordering and the optics, show that the {110} growth sector consists of triclinic disordered K-feldspar and the {001} and {01} sectors monoclinic high or low sanidine or orthoclase.

These observations indicate that the characteristic internal textures seen on all optical micrographs are formed during the process of crystal growth, and are not due to monoclinic-triclinic transition. Although the transition process has taken place to a slight extent, the original growth textures remain well preserved throughout geological time. It is suggested from these observations that the degree of Al/Si ordering is mainly controlled by the different rates of growth and the different two-dimensional atomic arrangements exposed on the various growth surfaces. The higher the growth rate the more disordered are the phases that form. The symmetry of the two-dimensional atomic arrangement is kept during growth regardless of the degree of ordering; {001} and {01} growth sectors whose crystal surfaces are parallel to b-axis are monoclinic, and the {110} sector whose surface is inclined to the b-axis is triclinic.
Stratiform magnetite crystals of abnormal morphology from volcanic carbonatites in Tanzania, Kenya, Greenland, and India
Authors: Deans T. , Seager A. F.
Published: December 2006

Magnetite is common in carbonatites, and usually has octahedral habit. Abnormal crystals from Galapo, Tanzania, were long thought to be unique, but such crystals are now known to occur at seven localities in four countries. The magnetite is titaniferous, but not unusual in composition for its provenance. The abnormal crystals typically have large growth pyramids extending in one direction (occasionally in two or more directions). They appear to be formed by superimposition of macroscopic growth sheets, parallel to octahedral and other planes, giving a planar structure to the growth pyramid. The edges of the sheets may form low-index or more complex surfaces. Some sheets project beyond the bounding planes of the growth pyramid, which is not repeated in crystallographically equivalent orientations. This unusual mode of growth will be called stratiform. Recognition of these distinctive crystals elsewhere might reveal the presence of hitherto unsuspected carbonatites.
Hydrous gem magnesian cordierite with inclusions of hydroxyapatite, dolomite, and rutile
Authors: Graziani Giorgio , Guidi Gioli
Published: December 2006

An uncommon sample of a pale-blue Madagascar cordierite and its mineral inclusions of different kinds have been studied. The physical properties of the embedding cordierite are: α = 1·528, β = 1·522, γ = 1·537, δ = 0·009, 2Vα = 96°, density = 2·534 g/cm3, a = 17·082 Å, b = 9·728, c = 9·352, Δ = 0·26. The electron probe analysis gave SiO2=48·64%, Al2O3 = 35·08, FeO = 0·70, MgO = 12·35, H2O+ = 2·50. This is therefore a hydrous magnesian cordierite. Its structural state is related to the shift in α, β, γ, 2Vα, and Δ with heating. Probe analyses were performed on the inclusions: hydro-xyapatite, dolomite, and rutile. The occurrence of dolomite suggests the conditions of formation of the host mineral.
Tin-rich garnet, pyroxene, and spinel from a slag
Authors: Butler B. C. M.
Published: December 2006

Garnet containing up to 26% SnO2, and pyroxene and spinel containing 12% and 10% SnO2 respectively, occur in a tin-refining slag in association with cassiterite. These tin contents probably represent minimum values for the limit of ionic replacement of Sn4+ in the structure of these minerals. The absence of tin from coexisting melilite suggests that Sn4+ is only able to substitute for ions in octahedral co-ordination.
The Dhajala meteorite
Authors: Das Gupta S. P. , Sen Gupta P. R. , Dube A. , Sen Gupta N. R. , Das Gupta D. R.
Published: December 2006

The Dhajala meteorite shower, the latest recorded fall in India, comprises pieces fragmented near the lower limit of the break-up zone. The meteorite is a chondrite consisting of silica-rich chondrules making up to 34 vol.%, and fine-grained, Fe-Ni metal-rich groundmass admixed with a few irregular lithic fragments. Dhajala contains olivine of variable compositions, ortho- and clinopyroxenes, troilite, kamacite, taenite, chromite, and clear to opaque glass; magnetite occurs only in the fusion crust. The chondrules, which are of variable shape, mineral composition, and texture, represent different stages of quenching, leading to incomplete crystallization of minerals and some degree of disparity between norm and mode. Lithophile elements are less in Dhajala than in average chondrites. Two chemical analyses of Dhajala are presented and it has 27·10% total iron and 2·38 % sulphur (maximum). Chemical and petrological data indicate that it is an H3 olivine-bronzite chondrite. Evidence for the crystallization of chondrules from melt is overwhelming. Some chondrules have been permeated by later troilite and NiFe from the groundmass, which might have crystallized directly from a gaseous environment.
A microscope-mounted drill to isolate microgram quantities of mineral material from thin and polished sections
Authors: Verschure R. H.
Published: December 2006

Several types of microscope-mounted drills have been described in literature to obtain pure mineral material from thin sections or polished sections (e.g. Granigg, 1915; Moritz, 1929; Haycock, 1931; Russanow, 1937; Machairas, 1967), but all of them appear to be of limited mechanical stability and reliability. This paper describes an improved drill to extract under the microscope minute quantities of pure material from thin or polished sections. The drilling is performed in a liquid (silicon-oil) to minimize loss of the drilled-out mineral powder. With the help of a micromanipulator the liquid, together with the borings, is drawn up into a microcapillary tube (less than 30 µm in diameter) made of Lindemann glass. For identification of the mineral powder the microcapillary is mounted in a Debye-Scherrer X-ray diffraction camera.
Paragenesis of hydrothermal mineralization in amphibolites and granulites around Porthkerris Point, the Lizard, Cornwall
Authors: Seager A. F.
Published: December 2006

A study of the post-metamorphic hydrothermal mineralization in the gabbros of the Lizard has already been published (Seager, 1971). The present paper extends the investigation of mineralization in the peninsula to an adjacent area, on the NE. coast around Porthkerris Point. Table 1 gives the more important events of the paragenesis. Calcite and adularia are the only common minerals; all others are scarce or rare.

The calcite that precedes and succeeds adularia is called early calcite and late calcite, respectively. Both early and late calcite occur in several generations differing in habit, fluorescence, and phosphorescence.
Rajite, naturally occurring cupric pyrotellurite, a new mineral
Authors: Williams S. A.
Published: December 2006

Rajite was found at Lone Pine, New Mexico, by R. A. Jenkins. It occurs as small (1.5 mm) crystals in rhyolite with mackayite, and may be a pseudomorph after teineite. Analysis gave CuO 18.4, 15.3, 18.0; TeO2 73.7, 79.8, 79.1; rem. (respectively) 7.9, 2.4, 2.3. Some CaO in samples 2 and 3: 2.5, 0.6%. This gives CuTe2O5, identical to the artificial compound prepared by Moret et al. (1969). Easily soluble in dilute acids; readily fusible.

Monoclinic P21/c with a = 6.866 Å, b = 9.314, c = 7.598, β = 109.1°. Strongest lines 3.064(10), 4.654(8), 3.348(8), 3.111(7), 2.744(7), 3.793(6B), 2.844(5), 2.796(5). With Z = 4, ρcalc = 5.77 g/cm3.

Crystals Duesbury green (RHS-131D), H = 4, ρmeas = 5.75 g/cm3. Pleochroic in greens γ > β > α; α = 2.115, β = 2.135, ‖ [010], γ = 2.26, α:[001] 22° in obtuse β, 2Vγ = 40°.
Kleemanite, a new zinc aluminium phosphate
Authors: Pilkington E. S. , Segnit E. R. , Watts J. , Francis G.
Published: December 2006

A new hydrated zinc aluminium phosphate mineral has the composition ZnAl2(PO4)2(OH)2.3H2O. It has been named kleemanite. It occurred rarely both as veinlets 1–2 mm thick, and as thin layers on surfaces of cracks and small cavities in one section of the iron ore deposit at Iron Knob, South Australia. Chemical, X-ray, thermal analysis, and optical data are given.
Georgeite, a new amorphous copper carbonate from the Carr Boyd Mine, Western Australia
Authors: Bridge P. J. , Just J. , Hey M. H.
Published: December 2006

Georgeite, an amorphous copper carbonatehydrate, has been found in the oxidation zone of the Carr Boyd nickel deposit, Western Australia. It forms thin coatings mostly associated with malachite and chalconatronite on partly weathered tremolite rock containing disseminated copper and iron sulphides.

Physical properties: Colour light blue, streak pale blue, lustre vitreous to earthy, fracture conchoidal, soft, sp. gr. 2.55; transparent to sub-opaque (aggregates), n(NaD) = 1.593, isotropic. Amorphous to X-rays and electron beam.

Chemical microanalysis gave (wt%) CuO 54.9, ZnO 0.4, Na2O 2.7, CO2 20.8, H2O 21.7, sum 100.5. After deduction of all Na2O and corresponding amounts of CuO, CO2, and H2O as chalconatronite (12.35 wt%) the atomic ratios correspond to an empirical formula (Cu5.0, Zn0.05)(CO3)3(OH)4.12.6.3H2O, the ideal formula being Cu5(CO3)3(OH)4.6H2O.
Mineralization at Seathwaite Tam, near Coniston, English Lake District: The first occurrence of wittichenite in Great Britain
Authors: Stanley C. J. , Criddle A. J.
Published: December 2006

Ore specimens from the abandoned copper mine at Seathwaite Tarn, Cumbria, were studied in polished section by reflected light microscopy. The mineral paragenesis is described and related to current views on Lake District ore genesis. A common origin with the neighbouring deposit at Coniston is proposed. Wittichenite was identified in the ore, and is the first authenticated occurrence in Great Britain.
Almandine pseudomorphous after plagioclase in a metadolerite dyke from the Jotunheim, Norway
Authors: Battey M. H. , Davison W. , Oakley P. J.
Published: December 2006

An undeformed metadolerite dyke cutting foliated pyroxene-granulite facies gneisses in the Jotunhelm, Norway, has almandine rods replacing the cores of plagioclase laths, although garnet is generally absent from the enclosing gneisses, and is not present in reaction zones between peridotites and gneisses. Chemical analyses of the dyke and its garnet, plagioclase, and clinopyroxene are given. The presence of garnet in the dyke is attributed to the low mg ratio of the rock. The nature of the reaction leading to garnet pseudomorphous after plagioclase is discussed.
Definitive data on bohdanowiczite, a new silver bismuth selenide
Authors: Banaś M. , Atkin D. , Bowles J. F. W. , Simpson P. R.
Published: December 2006

Bohdanowiczite was first described in 1967 but incomplete data prevented its acceptance as a new mineral at that time. Additional data on the same material now characterize bohdanowiczite as a new species with the formula:

3[(Ag0.98Cu0.02)0.97(Bi0.97Pb0.03)1.02(Se0.83S0.17)2.01]

The mineral occurs in intimate intergrowths with clausthalite and wittichenite in polymetallic mineralization at Kletno in Poland. In reflected light bohdanowiczite has a creamy-yellow colour and short polysynthetic twinning is frequently observed. Cell parameters indexed on a hexagonal lattice are a = 4.183±0.008 Å and c = 19.561± 0.016 Å. Pm1 is the most likely space group. The strongest lines of the powder pattern are 2.91(100), 2.03(30), 3.40(20), 6.54(20), 2.09(18), 3.26(18). The calculated density is 7.72 gm/cm3 and the VHN between 63 and 96 kg/mm2.
Serpentine minerals from veins in serpentinite rocks
Authors: Morandi N. , Felice G.
Published: December 2006

Crystal-chemical analyses of the serpentine polymorphs, sampled from macroscopic veins in the serpentinite rocks from Sasso della Mantesca and Sasso di S. Zanobi, are reported. The samples were examined by X-ray diffraction, thermal analysis (TG and DTG), scanning and transmission electron microscopy, IR absorption spectroscopy, microprobe, and chemical tests.

The results show: chrysotile 2Orc1 in tubular fibrils placed perpendicularly to walls of iso-oriented ‘lenticular veins’; and polygonal serpentine formed by flat layers of lizardite 2H and/or 1T, arranged as an outer shell of a central core of chrysotile 2Mc1 fibres; this type of serpentine with high crystallinity and unusual morphological development is included in ‘green veins’, which show variable Al, Fe, and Mg contents.

A genetic mechanism correlating the petrographic observations with the mineralogical results is discussed.
The effect of aluminium on the infra-red spectra of 7 Å trioctahedral minerals
Authors: Serna Carlos J. , White Joe L. , Velde Bruce N.
Published: December 2006

The substitution of 2A13+ for Si4+ +M2+ (M = Mg or Ni) has been studied by infra-red spectroscopy in 7 Å trioctahedral minerals over the composition range from Al = 0.00 to Al = 2.00. Significant differences are observed in the infra-red spectra and these make possible an estimation of the amount of Al in tetrahedral coordination. The most striking effect of the substitution is observed in the stretching vibrations of the outer hydroxyl groups and that of the silicate anion.

The aluminous Mg-serpentines can be readily distinguished from their analogues, the aluminous Niserpentines, by the absence of the Mg-OH absorption band between 570 and 615 cm−1 in the latter.
Distribution of Fe and Mg between garnet and biotite in Scottish Barrovian metamorphic zones
Authors: Baltatzis E.
Published: December 2006

The distribution coefficient KD = (Mg/ Fe)garnet/(Mg/Fe)biotite has been calculated for eight garnet-biotite pairs from rocks ranging from the garnet isograd to the staurolite zone along the Stonehaven coast of NE Scotland. This distribution coefficient depends upon metamorphic temperature and is not dependent upon the Mn and Ca content of garnet. Garnet-biotite geothermometer yields temperatures of about 500, 550, and 575–620°C for the garnet, chloritoid + staurolite, and staurolite zones respectively.
Geochemical aspects of the Santonian Chalk of Ramsgate, England, and the origin of the chert and clay minerals
Authors: Spears D. A.
Published: December 2006

The mineralogy and major-element geochemistry of thirty-seven samples from a borehole in the Upper Cretaceous Chalk (Santonian) of Kent has been determined. The mean carbonate content is 97% and the carbonate is a low-Mg calcite (0.42 mol % MgCO3). Most of the silica is deduced to be biogenic chert. The total clay content probably varies through the sequence due to changes in the rate of carbonate sedimentation. The clay composition remains relatively constant with smectite more abundant than illite. The smectite and K-feldspar could be formed from volcanic debris whereas illite and quartz are thought to be detrital.
Topaz occurrence in Mardan, north-west Pakistan
Authors: Jan M. Qasim
Published: December 2006

Synopsis

Colourless, purple, and pink topaz and transparent quartz crystals have been found in calcite veins (with or without milky quartz) in calcareous rocks near Katlang (34° 24′ N, 72° 6′ E), Mardan district. The veins do not contain any fluorite nor the country rocks any topaz. The topaz and transparent quartz crystals are mostly broken and perfectly euhedral outlines are very rare. Refractive indices, 2V, specific gravity, and the fluorine (determined) and H2O + (calculated) contents of two topaz crystals are suggestive of their high 100 OH/(OH+F) ratios (> 25). Rather than being derived, the topaz may have formed in situ by hydrothermal/pneumatolytic activity, followed by tectonic movements that fractured the crystals and resulted in their incorporation in later-formed vein calcite.
Alluaudites, wyllieites, arrojadites: crystal chemistry and nomenclature
Authors: Moore Paul B. , Ito Jun
Published: December 2006

Synopsis

A nomenclature is proposed for the alluaudite and wyllieite complex series which is based on sequentially distributing the cations in the cell according to increasing polyhedral size, matching that size with increasing ionic radii of the cations. For oxidized members, the largest site may be partly occupied to empty after all the cations have been distributed. This is supported by structural study.

For alluaudites, the cell formula is X(2)4X(I)4 M(I)4M(2)8(PO4)12 and is written according to decreasing size of the discrete sites. The X(I) and X(2) sites are appended as suffixes in the trivial nomenclature, that is specific name—X(I)X(2).

For wyllieites, the cell formula is X(2)4X (1a)2X(1b)2M(I)4M(2a)4A14(PO4)12. The X(1a), X(1b), and X(2) sites are appended as suffixes in the trivial nomenclature, that is specific name--X(la) X(Ib)X(2).

The nomenclature proposed is:

Seventeen analyses are discussed (of which five are new) for alluaudite and four analyses (of which three are new) for wyllieites. Their distribution is given parenthetically above. One analysis revealed predominant Mg2+ in M(2). It is named maghagen-dortite.

Six new analyses are presented for the arrojadite family of minerals including re-examination of dickinsonite from Branchville, Connecticut. Al3+ is always present. We propose X1 Al (OH,F)(PO4)12, Z = 4, where X = large cations (K+, Ba2+, Pb2+, etc.), Y = Na1+, Ca2+, and M = Fe2+ Mn2+, Mg2+. A range of cations X, Y, M, and Al between 76.8 and 85.9 in the cell (84 for proposed formula) suggests the likelihood of some vacancies in the structure.
The blue coloration in banded fluorite (Blue John) from Castleton, Derbyshire, England
Authors: Galwey A. K. , Jones K. A. , Reed R. , Dollimore D.
Published: December 2006

From the microscopic examination of lightly etched, cleaved (111) surfaces of banded blue fluorite (Blue John, from Castleton, Derbyshire) it is concluded that the coloured lamellae are not necessarily or exclusively associated with lattice-line imperfections. Elemental analyses, by electron dispersive methods, of fresh cleavage (111) surfaces in the immediate vicinity of small inclusions (c. 10 µm diameter) possessing associated coloured haloes detected no appreciable concentrations of impurities. From the evidence available, it is suggested that the zones of blue colour consist of colloidal calcium resulting from radiation damage caused by the intermittent deposition of radioactive material on the surfaces of fluorite during crystal development. The dispersion of colloidal calcium produced is particularly stable as a consequence of the close correspondence between lattice spacings in calcium fluoride and in calcium metal.
Electron petrography of high-temperature oxidation in olivine from the Rhum Layered Intrusion
Authors: Putnis A.
Published: December 2006

Electron-microscope observations of the oxidation products of olivine suggest that oxidation results in the formation ofplatelets of an ‘oxidized olivine’ phase, which has a superstructure of the olivine structure. Subsequently this intermediate phase breaks down by a cellular decomposition process to a eutectoidal intergrowth of magnetite and pyroxene. This intergrowth is responsible for the dendritic magnetite inclusions commonly observed in some olivines from Rhum.
The development of porous microstructures during the dehydration of boehmite
Authors: Wilson S. J.
Published: December 2006

Electron-microscope observations have been used to follow the low-temperature dehydration of boehmite, and show that a coherent skeleton of γ-Al2O3 with a porous texture is produced. For material fired in air the development of a number of pore systems is described. Of these the most important, as far as the dehydration process is concerned, is a lamellar pore system parallel to (001)γ and having a regular spacing of the order of 35–40. Å. A much faster dehydration process is induced by exposure to the electron beam and results in the formation of a more randomly oriented pore structure. The observed microstructure and the calculated internal surface area are compared with the results of previous adsorption studies.
Coexisting pyroxenes from spinel pyroxenites from the Eastern Ghats of Andhra Pradesh, India
Authors: Rao A. T. , Raman C. V. , Appa Rao G.
Published: December 2006

Synopsis

Analyses are given of four pairs of coexisting pyroxenes; theirKpranges from 1.282 to 1.369, suggesting equilibration temperatures as high as 1200 °C and pressures of the order of 8 to 9 kb.