bluuebunny/crossref_metadata_2025_split huggingface dataset:
The uranium-bearing mineral bolivarite: new data and a second occurrence
Authors: Van Wambeke L. 
Published: December 2006

SummaryA second occurrence of the mineral bolivarite has been found in the Kobokobo pegmatite, Kivu, Republic of Congo (Kinshasa). This amorphous mineral was previously considered to be evansite. Its physical properties are: weak birefringence; biaxial to uniaxial positive; n = 1·50–1·51; specific gravity 1·97–2·05; hardness 3 to 3½.Three chemical analyses have been performed on the Congolese material. The general formula of the mineral is Al2(PO4)(OH)3.4–5 H2O. Both known bolivarites from Spain and Congo contain abnormal amounts of U. The bright green UV fluorescence is due to the presence of U. The DTA curve of the Congolese bolivarite is given. Its genesis is discussed. This uranium-bearing mineral may be an indicator of uranium mineralization in Spain.
Chemical changes accompanying spherulitic crystallization in rhyolitic lavas, Central Volcanic Region, New Zealand
Authors: Ewart A. 
Published: December 2006

SummarySpherulitic devitrification is a post-eruptive process affecting many rhyolitic lavas of the Taupo region. The spherulites consist of cryptocrystalline intergrowths ofα-cristobalite and alkali feldspar (calcic anorthoclase), with minute granules of magnetite, hematite, and secondary (?)goethite. The effects of chemical fractionation occurring during progressive spherulite growth has been studied from a suite of samples from the Aratiatia rhyolite. The most significant effect is the progressive enrichment of both bulk spherulite compositions and the coexisting residual glass in potash with increasing spherulite development. This effect is due both to the very low potash in the earliest formed spherulites and to the consistently higher Na/K ratios of the spherulites relative to the total rock compositions. These differences progressively decrease with increasing spherulite crystallization. The bulk rock compositions, however, evidently remain essentially constant. The degree of potash enrichment in the residual glasses during advanced stages of devitrification is greater than expected by reference to the ternary feldspar and quartz-feldspar systems. This post-eruptive alkali fractionation during spherulite formation is superimposed on the pre-eruptive phenocryst-liquid fractionation.
The origin of the granitic sheets and veins in the Loch Coire migmatites, Scotland
Authors: Brown P. E. 
Published: December 2006

SummaryMost of the granitic sheets and veins in the Loch Coire migmatite complex do not have chemical compositions in accordance with a formation by local anatexis. Regional metasomatism by fluids from outside the exposed confines of the complex was an important factor in the development of the sheets and veins, although there was probably some overlap with magmatic conditions.
Calc-aluminous insets in olivine of the Sharps chondrite
Authors: Dodd R. T. 
Published: December 2006

SummaryA 250 µm olivine crystal in Sharps contains 1 to 5 µm insets identified by microprobe analysis as ferroan monticellite, spinel, and fassaite with average compositions: olivine (host), (Fe0·44Mg1·51Ca0·05) (Si0·99Al0·01)O4; ferroan monticellite, (Ca0·89Fe0·41Mg0·66) (Si1·00Al0·02)O4; spinel, (Fe0·41Mg0·59)(Fe0·063+Cr0·23Al1·69Si0·01Ti0·01)O4; and fassaite, Ca0.96(Fe0·01Mg0·59)(Al0·18Ti0·07Fe0·163+)(Si1·53Al0·47)O6. Textural and experimental data suggest early crystallization of spinel from a calcic olivine melt, exsolution of ferroan monticellite from the host olivine, and reaction of spinel and ferroan monticellite to form fassaite. The severe depletion of alkalies and silica in this crystal suggests it is a residue from vapour fractionation.
The cause of coloration in Derbyshire Blue John banded fluorite and other blue banded fluorites
Authors: Mackenzie K. J. D. , Green J. M. 
Published: December 2006

SummaryThe cause of coloration of Blue John fluorite from Castleton, Derbyshire, and blue banded fluorites from Ashover, Derbyshire, and Weardale, Co. Durham, has been investigated by a number of techniques, including mass spectrometry, optical spectroscopy, and paramagnetic resonance measurements on natural and irradiated samples. In all respects Blue John is indistinguishable from the other blue banded fluorites. Although traces of hydrocarbons were found in all the natural fluorites including Blue John, they are shown not to be the cause of the colouration. The optical spectra and bleaching behaviour are consistent with colouration by colloidal calcium rather than F-centres. The causes of colour banding are discussed.
The join CaMgSi2O6-Ca2MgSi2O7-CaTiAl2O6 in the system CaO-MgO-Al2O3-TiO2-SiO2 and its bearing on titanpyroxenes
Authors: Onuma Kosuke , Yagi Kenzo 
Published: December 2006

SummaryThe phase equilibrium diagrams of CaMgSi2O6-CaTiAl2O6 with 10, 20, and 30 wt % Ca2MgSi2O7 in the join CaMgSi2O6-Ca2MgSi2O7-CaTiAl2O6 were determined. Six three-phase assemblages, six four-phase assemblages, and two five-phase assemblages (isobaric trivariant, divariant, and univariant) were confirmed. The univariant assemblages are diopsidess+forsterite+åkermanitess + perovskite + liquid and diopsidess+åkermanitess+perovskite+spinel + liquid. Because of the complex solid solutions of diopside and åkermanite the crystallization ceases before invariant assemblages are reached and the final phase assemblage in the diopside-rich region is diopsidess+åkermanitess+perovskite, in the diopside-poor region diopsidess+åkermanitess+perovskite + spinel. Two invariant points, diopsidess+forsterite+åkermanitess+perovskite+spinel+liquid and diopsidess+åkermanitess+anorthite+perovskite+spinel+liquid in the silica-poor region of the system CaO-MgO-Al2O3-TiO2-SiO2 are estimated. The diopside solid solution in this join is discussed with its bearing on the natural titanpyroxenes from alkalic rocks including melilite.
The synthesis of birnessite, cryptomelane, and some other oxides and hydroxides of manganese
Authors: McKenzie R. M. 
Published: December 2006

SummaryDetailed methods are described for the laboratory preparation of the manganese minerals manganosite, hausmannite, manganite, partridgeite, birnessite, cryptomelane, pyrolusite, and todorokite. New data are presented on the conversion of birnessite to cryptomelane, and on the exchange properties of potassium in these two minerals. It was found that the upper limit of potassium in cryptomelane is about 7 % K, while the lower limit lies between 0·25 % and 2·2 % K.
The composition of anomalous plagioclase glass and coexisting plagioclase from Mistastin Lake, Labrador, Canada
Authors: Currie K. L. 
Published: December 2006

SummaryAnorthosite country rocks near the fissure vents of an andesitic resurgent caldera contain coexisting crystalline plagioclase, pseudomorphous plagioclase glass, and anomalously dense, massive plagioclase glass. Glass pseudomorphous after labradorite (An 53) has the composition of oligoclase (An 17). Large masses of dense plagioclase glass have compositions near An 53, but relict crystalline plagioclase within them has compositions near An 80. Devitrification products of this glass have potassium-rich compositions. These compositions are compatible with partial thermal melting in a high-temperature, moderate-pressure pulse. Such a pulse might be asscciated with a confined chemical explosion.
Charge-transfer in ferromagnesian silicates: The polarized electronic spectra of trioctahedral micas
Authors: Robbins D. W. , Strens R. G. J. 
Published: December 2006

SummaryPolarized spectra (2000 to 25000 Å) have been obtained for fifteen analysed trioctahedral micas covering a wide range of compositions, and including four phlogopites, nine biotites, and two lepidomelanes. Three main contributions to the absorption have been noted: charge transfer from oxygen to ferrous iron throughout the visible and near ultraviolet, charge transfer from ferrous to ferric ions at the red end of the visible spectrum and internal d-d transitions of ferrous ions in the near infrared.Substitutions in the brucite layer (especially Ti) cause the O → Fe2+ band to broaden, and thus to encroach on the visible region for vibration directions in the plane of the cleavage flake. The transmission window between these bands is further blocked by the Fe2+ → Fe3+ charge-transfer band, which is polarized in the plane of the flake. The overall effect is to produce very strong absorption throughout the visible region for (β, γ) vibration directions, and relatively weak absorption for α, i.e. the observed very strong pleochroism of biotite.Many features of the spectra of chlorite, amphiboles, and tourmaline, which contain octahedral ions in brucite-like sheets, strips, and fragments respectively, may be interpreted by analogy with biotite.Two types of solid solution effect are described: substitutional broadening, which is responsible for the extension of the O → Fe2+ band into the visible region in biotites and aluminous ortho-pyroxenes, and substitutional intensification, which permits in solid solutions transitions that are forbidden by the conventional selection rules.
Myrmekite and muscovite developed by retrograde metamorphism at Broken Hill, New South Wales
Authors: Phillips Evan R. , Ransom D. M. , Vernon R. H. 
Published: December 2006

SummaryRetrograde metamorphism of gneisses and pegmatites leads in part to the destruction of feldspar and its replacement by late-stage lobate myrmekite and muscovite. Reactions promoted by retrogression suggest a range in volume of quartz production that may supplement that developed by exsolution and lead to deviations from the strict proportionality relationship suggested by previous workers. There is no need, however, to propose that quartz in myrmekite originates by constriction of pre-existing quartz within exsolved albite.
Natural garnet-pyroxene transformation in Cenozoic alkali basalt from Nigeria?
Authors: Wright J. B. 
Published: December 2006

SummaryAggregates of clinopyroxene in some doleritic lavas have external outlines strongly reminiscent of garnet crystals. They cannot be satisfactorily identified either as Upper Mantle fragments or as cognate synneusis aggregates, and it is suggested that they may have developed by inversion from original garnets, which crystallized at very high pressures. Neither morphology nor composition can provide conclusive proof of their original nature, but there is circumstantial evidence from the presence of an unusual inclusion suite in basalts nearby. The commonest phases are zircon and corundum, minerals more usually found in kimberlites than in basalts. Corundum in kimberlite inclusions is almost invariably accompanied by calcium-rich garnet, which adds some significance to the suggestion that these clinopyroxene aggregates are pseudomorphing original garnet.
Thermal decomposition of amosite, crocidolite, and biotite
Authors: Rouxhet P. G. , Gillard J. L. , Fripiat J. J. 
Published: December 2006

SummaryThe oxidation of amosite, crocidolite, and biotite has been determined at temperatures up to nearly 900 °C under both a vacuum (10−2 mm Hg) and oxygen (10 and 600 mm Hg). Infrared spectra gave the loss of constitutional hydroxyl under these conditions. The loss of tensile strength of the amphiboles with increasing temperature seems to be due to thermal decomposition. For the three minerals oxidation takes place progressively over a broad temperature range. Under vacuum there is a certain temperature above which the ferric iron previously formed is reduced; this temperature corresponds to the completion of the loss of hydroxyl. The crocidolite anhydride in the literature is most probably an oxycrocidolite formed by dehydrogenation, the truly dehydroxylated zones being amorphous.
The thermal expansion behaviour of the framework silicates
Authors: Taylor D. 
Published: December 2006

SummaryThis paper gives a revision and expansion of an earlier interpretation of the thermal expansion behaviour of the framework silicates. The partially-collapsed and ideal fully-expanded structures of quartz, cristobalite, and sodalite are characterized by the geometric relationship between the angle of rotation of their tetrahedra from the ideal fully-expanded state, their cell parameters, and the length of the tetrahedron edge. Their thermal expansion behaviour is interpreted as due mainly to the effect of the rotation of the tetrahedra towards the fully-expanded state modified by anisotropic thermal motion of the framework oxygens and distortion of the tetrahedra from a regular form. With the leucite and sodalite groups the significance of the interframework cations is discussed.
Study of metamict Ceylon zircons
Authors: Vance E. R. , Anderson B. W. 
Published: December 2006

SummaryX-ray, density, refractive index, and optical absorption measurements have been made on metamict Ceylon zircons. The appearance of a previously reported anomalous optical absorption spectrum in low Ceylon zircons has been associated with small particles of cubic or tetragonal zirconium dioxide in a radiation-damaged zircon lattice, in both heated and unheated stones. No evidence of a previously reported second phase was detected in intermediate Ceylon zircons.
Titrimetric analysis for silicon
Authors: Kalocsai G. I. Z. , Hockley J. J. 
Published: December 2006

SummaryRapid, accurate silica determinations have been made titrimetrically following decomposition by HClO4-HF in a ‘Teflon’ vessel, the volatilized silicon tetrafluoride being precipitated as K2SiF6 in a HF-KF-glycerol-alcohol mixture. After filtration and washing with alcohol the precipitate is dissolved in boiling water, then titrated with NaOH. This method has many advantages over conventional gravimetric or spectrophotometric procedures.
Structure and twinning in
spencerite
Authors: Fanfani L. , Nunzi A. , Zanazzi P. F. 
Published: December 2006

Summary
A refinement of the crystal structure of
spencerite,
Zn4(PO4)2(OH)2·3H2O,
was performed on a twin crystal from Salmo,
British Columbia. Three-dimensional intensity data
were collected by a Weissenberg apparatus. The
R index was 0·098 for
335 independent observed reflections. The crystal
structure previously determined is essentially
confirmed. Co-ordination around Zn is both
octahedral and tetrahedral. The atomic arrangement
consists of complex sheets of co-ordination
octahedra and tetrahedra around Zn and P atoms
connected by layers of water molecules. The
frequent occurrence of twinning in spencerite is
explained from structural considerations.
The crystal structure of stilpnomelane.
Part II. The full cell
Authors: Eggleton R. A. 
Published: December 2006

Summary
The structural formula of stilpnomelane
averaged from 37 representative literature
analyses and based on the determined structure is
(Ca,Na,K)4(Ti0·1Al2·3Fe35·5Mn0·8Mg9·3)[Si63Al9](O,OH)216·nH2O.
Ferrostilpnomelanes have up to 12
R3+
cations in the octahedral sheet,
ferristilpnomelanes commonly have between 24 and
30
R3+
cations, rarely up to 37. The two groups can be
distinguished by accurate X-ray powder
diffraction, ferrostilpnomelanes having
d001
less and a greater than
have ferristilpnomelanes. The unit cell is
triclinic, a =
b∼21·8 Å,
γ = 120°,
d001∼12·2
Å,
P.
Hexagonal groups or ‘islands’ of 24 silicon-oxygen
tetrahedra co-ordinate to the octahedral sheet,
the centres of the ‘islands’ are displaced by
5a/12,
8b/12 on either side of
the octahedral sheet as a result of warping of
this sheet to permit articulation with the smaller
tetrahedral sheet. The 24-tetrahedra ‘islands’ are
linked laterally by 6-member rings of inverted
tetrahedra, which in turn link at their apices to
like rings connecting the next sheet of ‘islands’.
Thus a single tetrahedral layer is 4 tetrahedra
thick and has symmetry
6/m. The 6-member rings
of tetrahedra act as hinges permitting up to 0·5 Å
extension or contraction of the tetrahedral sheet
to accommodate variations in the octahedral sheet
dimensions with varying
R2+/R3+
ratio.
A metallographie study of some iron
meteorites of high nickel content
Authors: Axon H. J. , Smith P. L. 
Published: December 2006

Summary
A metallographic investigation of macro-
and microstructure, supported in some instances by
microprobe examination, has been made on a number
of nickel-rich iron meteorites from the British
Museum Collection. Monahans, Wiley, Cowra, and
Deep Springs are considered together as plessitic
irons rather than ataxites, whilst Morradal shows
an unusual and coarse plessitic structure that has
been altered by pre-terrestrial shock and
reheating. Cape of Good Hope, Hoba, Tlacotepec,
and Chinga show chemical and structural
similarities and are discussed together, as are
Weaver Mountains, Klondike, and Warburton Range.
Meteorites considered separately include Kokomo,
Piñon, Shingle Springs, South Byron, San
Cristobal, Lime Creek, and Santa Catharina.
Particular attention is paid to the presence of
sulphides and of phosphorus-containing phases and
their influence on the formation of the macro- and
microstructure of these meteorites. Patches of
oriented sheen form a macroscopic feature of the
Cape of Good Hope group of irons and this effect
is considered in relation to details of the
microstructure. Attention is drawn to the fact
that in Cowra, Piñon, Weaver Mountains, South
Byron, and Morradal the troilite appears to have
been remelted and dispersed by a shock event that
operated at a temperature sufficiently high to
allow obvious shock damage to anneal out of the
metal phases.
Rameauite and agrinierite, two new hydrated complex uranyl oxides from Margnac, France
Authors: Cesbron F. , Brown W. L. , Bariand P. , Geffroy J. 
Published: December 2006

SummaryTwo new hydrated uranyl oxides from Margnac, France, are described. Rameauite, K2O.CaO.6UO3.9H2O, occurs with uranophane and calcite on pitchblende, agrinierite, 2(K2O, CaO,SrO). 6UO3.8H2O, with uranophane in small cavities in ‘gummite’.Rameauite is monoclinic with a 13·97, b 14·26, c 14·22 Å, β 121° 1′±5′; the space group is C2/c. The principal d-spacings, with hkl values and relative intensities, are: 7·12, 020, vvs; 3·566, 040, vs; 3·495, 40, vvs; 3·473, 202, vs; 3·185, 22, vs; 3·139, 42, vvs; 2·993, 400, vvs; 2·495, 44, ms. Measured density 5·6 g.cm−3. The orange crystals are twinned on {100}, flattened on {010} and elongate parallel to [001]; there is a good {010} cleavage. α ‖; [010], γ: [001] 4 to 6° in the obtuse angle β, 2Vα 32°; the two principal reflectivities for yellow light on {010} are 10·6 and 10·4%. The main endothermic peaks on the d.t.a. diagram are at 95, 130, and 170 °C (loss of water), and at 1050 °C (loss of oxygen).Agrinierite is orthorhombic with a 14·04, b 24·07, c 14·13 Å; space group Cmmm on the assumption of holohedral symmetry. Measured density 5·7 g.cm−3. The principal d-spacings are 7·08, 002, vvs; 6·05, 220, ms; 3·516, 400 & 332, s; 3·485, 062 & 260, vs; 3·153, 204 & 134, vs; 3·128, 262, vvs; 2·023, 660, s. The orange crystals are tabular on {001} with pseudo-hexagonal section bounded by the trace of (010), and show sector twinning on {110} as in billietite; there is a good {001} cleavage. The two reflectivities for yellow light on the face (001) are 12·0 and 11·2 %, corresponding to a refractive index of about 2. α ‖ [001], γ ‖ [010], 2Vα 55°. The principal endothermic d.t.a. peaks are at 163 °C (loss of water) and 1060 °C (loss of oxygen).Rameauite is named after J. Rameau and agrinierite after H. Agrinier. The original specimens are deposited in the Mineralogical Collection of the University of Paris VI.
The new mineral insizwaite (PtBi2) and new data on niggliite (PtSn)
Authors: Cabri L. J. , Harris D. C. 
Published: December 2006

SummaryInsizwaite from Waterfall Gorge, Insizwa, is a new mineral with the composition Pt1·00Bi1·35Sb0·57. The name is for the locality and is to be applied to the end member PtBi2. The analysed material is an antimonian variety. The mineral is cubic, the unit-cell for the antimonian variety has a 6·625 (2) Å, probable space group Pa3, calc. D 12·8 g/cm3. The strongest lines on the X-ray diffraction powder pattern are: 2·96 (8) 210; 2·70 (8) 211; 2·34 (5) 220; 1·99 (10 311; 1·774 (7) 321; 1·433 (5) 421; 1·277 (6) 511, 333; 1·171 (6) 440; and 0·862 (7) 731. Under reflected light the mineral is white (in air and in oil) and is isotropic. Reflectance measurements at 470, 546, 589, and 650 nm gave 61·1, 60·0, 60·6, and 61·7 %. Micro-indentation hardness values range from 488 to 540 (av. 519) kg/mm2 with a 25 g load.New data are presented for niggliite from the type locality and for synthetic PtSn.
A differentiated ultrabasic sheet on Sgurr Dearg, Isle of Skye
Authors: Gibb Fergus G. F. 
Published: December 2006

SummaryThe field relations, mineralogy, and petrography of a small Tertiary ultrabasic sheet are briefly described. Chemical analyses show that compositional variations exist within the intrusion and electron-probe analyses demonstrate that optically undetectable zoning is present in the olivine. Throughout the intrusion, which is composed primarily of forsteritic olivine, calcic plagioclase, and clinopyroxene, there is a differential distribution of olivine. This distribution is attributed to flow differentiation during intrusion followed by gravitative sinking of olivine crystals.
Natural and laboratory α-particle irradiation of diamond
Authors: Vance E. R. , Milledge H. J. 
Published: December 2006

SummaryTo produce a lattice expansion readily detectable by conventional X-ray photographic means in α-irradiated diamond, a dose of order 1018α.cm−2 is required. Such a dose could be produced by pitchblende in ∼2 × 108 yr. and a previously reported lattice expansion in a natural diamond could therefore have occurred by long-term contact with a radioactive material. α-particle doses greater than ∼1014 cm−2 produce observable green colouration on the surface of an initially colourless diamond.
Iron—titanium oxide minerals in the Series,
Kap Edvard Holm, East Upper Layered
Greenland
Authors: Elsdon R. 
Published: December 2006

Summary
Electron-probe data are presented for
coexisting magnetite and ilmenite from seven
gabbro cumulates and a gabbro pegmatite, and bulk
FeO-Fe2O3-TiO2
analyses for ten magnetite-ilmenite assemblages.
The oxides equilibrated at 580 to 720 °C and
oxygen fugacities of 10−15·0
to 10−20·5 bar. Late-stage
alteration, associated with growth of hydrothermal
silicates, resulted in the breakdown of ilmenite
to rutile and the dissolution of magnetite. Higher
levels in the intrusion equilibrated at lower
temperatures than deeper levels. All features
described are consistent with the retention of the
initial water content of the magma within the
walls of the intrusion.
Biphosphammite: a second occurrence
Authors: Pryce M. W. 
Published: December 2006

Summary
Biphosphammite,
NH4H2PO4,
recorded once as secondary powder in 1870, occurs
with bat guano in Murra-el-elevyn cave, 31° 20′
S., 126° 0′ E., Western Australia.
The mineral occurs as tapering tetragonal
prisms with pyramidal terminations, which are
colourless to light buff, very soft, water
soluble, contain fine syngenite inclusions, and
have D 2·04, ω 1·525,
ε 1·480 Space group.
,
a 7·4935 Å,
c 7·340 Å, six
strongest powder X-ray lines 3·75 Å (10) 200; 5·24
Å (9) 101; 3·02 Å (9) 112; 1·993 Å (8) 312,213;
2·65 Å (7) 220; 2·368 Å (7) 310,301. Partial
analysis of purest available material gave:
P2O5
51·1, K2O 14·2,
(NH4)2O
12·3, SO2 5·59,
Na2O 0·16, water-insolubles
0·81 per cent, remainder mainly CaO and
H2O. Calculated mineral
content is 88 % biphosphammite (62 %
NH4H2PO4,
38% isomorphous
KH2PO4),
11·5% syngenite, insolubles 0·81 % calc. total
100·3 per cent.
Material proposed to be neotype is
preserved at the Government Chemical Laboratories,
Perth, Western Australia.