bluuebunny/crossref_metadata_2025 huggingface dataset:
The Wiluna Meteorite fall, Western Australia—2 September 1967
Authors: McCall G. J. H. , Jeffery P. M.
Published: December 2006

The fall of a shower of meteorites numbering several hundred fragments at Wiluna, Western Australia, on the night of 2 September 1967, has been investigated. Although the dispersion ellipse had been largely obscured by removal of fragments before a party of scientists were able to make a field investigation, it has, nevertheless, been possible to make a reasonable estimate of the shower distribution pattern. In spite of this removal of fragments, a number of pieces of meteorite were still found in situ. The bulk of the total recovery is in the collections of the Western Australian Museum, and the physical characteristics of these masses and their petrography is described. In all, some 490 individual fusion-crust coated stones and a large number of broken stony fragments are known to have been recovered. The meteorite is an olivine bronzite chondrite remarkably rich in discrete nodules of nickel iron, up to an inch across, commonly aggregated with troilite. A full chemical analysis of this fresh meteoritic material has been supplied by the British Museum (Natural History).
The petrology and chemical composition of a tholeiite sill on Schaapkraal 68JT, Lydenburg District, Transvaal, South Africa
Authors: Frick C.
Published: December 2006

A glass-bearing dolerite, which consists of orthopyroxene phenocrysts (γ 1·689, α 1·678, β 1·680, 2Vα 81°, S.G. 3·35) and a glassy mesostasis (n 1·568, S.G. 3·25), is described petrologically. Three new chemical analyses are given. From the petrological and chemical data it can be concluded that the orthopyroxene formed under intratelluric conditions and probably under high pressure. According to the recalculated chemical analysis of the orthopyroxene 0·22 Al3+ is in the Y position and much less Al3+ in the Z position. The chemical analysis of the residual glass is compared with similar residual glasses, and it shows that iron enrichment characterizes the earlier stages of crystallization differentiation, whereas the later stages are marked by an increase in Si4+, K+, and Na+.
The crystal structure of kilchoanite, Ca6(SiO4)(Si3O10), with some comments on related phases
Authors: Taylor H. F. W.
Published: December 2006

The crystal structure of kilchoanite, Ca6(SiO4)(Si3O10), has been determined from three- dimensional X-ray methods (r = 0·089 on 348 independent reflections). It is closely related to that of γ-Ca2SiO4, which is olivine-like. In kilchoanite, slabs of γ-Ca2SiO4 structure alternate with ones composed of Ca ions and finite chains of three tetrahedra; these have the composition Si3O108− and have rarely been observed previously. A related, synthetic phase, 8CaO. 5SIO2, probably has a similar structure but with a higher proportion of γ-Ca2SiO4 regions, and should thus be formulated as Ca8(SiO4)2(Si3O10). Disordered synthetic phases also occur that appear to have similar structures with still higher proportions of γ-Ca2SiO4 regions. These phases collectively form an interesting contrast to the chondrodite minerals.
Studies on manganese-bearing silicate minerals from metamorphosed manganese formations of india. II. Blanfordite, manganoan diopside, and brown manganiferous pyroxene
Authors: Roy Supriya
Published: December 2006

Three members of the pyroxene group, blanfordite, manganoan diopside, and brown manganiferous pyroxene, form important constituents of the manganese silicate rocks (gondite) of the metamorphosed manganese formations of India. The chemical composition of blanfordite is variable within the diopside-acmite series, that of the manganoan diopside corresponds to the diopside end of this series, and the brown manganiferous pyroxenes are related to aegirine-augites. The majority of the blanfordites studied have a composition within the aegirine-augite field, so that compositionally most of the blanfordites and brown manganiferous pyroxenes are similar in spite of the difference in their pleochroic schemes; The chemical composition of blanfordite varies: in association with calc-magnesian metasediments it has a high percentage of diopside, whereas in gondites and pegmatites its composition approaches more towards the acmite end. The blanfordites are often associated with manganiferous amphiboles such as juddite (manganoan magnesioriebeckite) and winchite (richterite-tremolite with blue and pink pleochroism) but never with tirodite. The brown manganiferous pyroxenes, on the other hand, are associated intimately with tirodite (richterite-tremolite with pleochroism in shades of yellow) but never with winchite and juddite.
On lithium and sodium trivalent-metal pyroxenes and crystal-field effects
Authors: Brown W. L.
Published: December 2006

Of the metals in the series Sc, V, Cr, Mn, Fe, and Ga pyroxenes of the type LiM3+Si2O6 were obtained only from Sc, V, Cr, and Fe in dry synthesis experiments near 1000 °C. Ga and A1 gave keatite derivatives (so-called ‘β-spodumenes’) by dry heating; α-Ga-eucryptite was obtained from Ga hydrothermally at pressures between 4·5 and 6·5 kb. Mn gave Mn2O3. The lattice parameters of the pyroxenes vary irregularly with atomic number. This variation and the failure to produce a Mn3+-pyroxene can be explained by the crystal-field theory. At high temperatures A1 and Ga are too small to stabilize a silicate pyroxene phase even at moderately high pressures and form less dense tectosilicates. The octahedral stabilization energy for Cr3+ ensures that Cr, which has the same size as Ga, forms a pyroxene.
Clinopyroxenes from the Upper Layered Series Kap Edvard Holm, East Greenland
Authors: Elsdon R.
Published: December 2006

Chemical compositions, unit-cell contents, and optical properties of six clinopyroxenes from the Upper Layered Series are presented. There is a gradual enrichment in iron upwards in the intrusion although there is no measurable effect on the optical properties, possibly because of Cr variation and exsolution of Fe and Ti as oxides. The chemistry of the clinopyroxenes is consistent with crystallization from a water-rich magma of transitional nature between tholeiite and alkali-olivine basalt. X-ray oscillation photographs of single crystals reveal the presence of sub-microscopic exsolution lamellae of pigeonite, a feature consistent with the transitional nature of the parent magma. Exsolution lamellae of titanomagnetite are ubiquitous and were formed at subsolidus temperatures in response to high buffered oxygen fugacity. Comparisons are made between the properties of clinopyroxenes from the Lower, Middle, and Upper Layered Series, and the conditions of crystallization of each series.
Piemontite schists from Haast River, New Zealand
Authors: Cooper A. F.
Published: December 2006

Piemontite-bearing metachert horizons are recorded from regionally metamorphosed eugeosynclinal rocks at Haast River, in the Southern Alps of New Zealand. Piemontite schist mineralogical assemblages produced by epidote-amphibole facies metamorphism are described petro-graphically, and are compared with lower grade occurrences in the Haast Schist Group.

A chemical analysis yields a composition of (Ca1·75Mg0·02Mn0·25Na0·03K0·01) (Al2·23Fe0·53Mn0·24 Ti0·01)Si3·06O12(OH)0·9, which is compared graphically with other metamorphic, hydrothermal, and metasomatic piemontites.

Single-crystal Weissenberg and powder camera X-ray data are given, and an attempt made to relate these X-ray parameters to chemical variation within the piemontite composition range.
A redetermination of the unit-cell geometry of scolecite
Authors: Smith G. W. , Walls R.
Published: December 2006

A re-examination of the mineral scolecite has shown that the previously published monoclinic (pseudo-orthorhombic) unit cell is face-centred and that the Hermann-Mauguin spacegroup symbol has been incorrectly assigned. The reduced monoclinic cell yields a 9·85 Å, b 18·98 Å, c 6·52 Å, β 110° 61; space group Aa. New indexed powder data are included.
Evidence for loss of protons and octahedral iron from oxidized biotites and vermiculites
Authors: Farmer V. C. , Russell J. D. , McHardy W. J. , Newman A. C. D. , Ahlrichs J. L. , Rimsaite J. Y. H.
Published: December 2006

Infra-red examination of a weathered biotite and of biotites that have been converted to vermiculites and subsequently oxidized, indicates that oxidation of octahedral ferrous ions to ferric ions is associated with a reversible conversion of hydroxyl ions to oxide ions. Subsequently, in high-iron biotites, there is an irreversible loss of ferric ions from the octahedral layer, resulting in an increased number of dioctahedral sites. Electron microscopy and X-ray diffraction indicate that ejected ferric ions form either amorphous interlayer oxides or, when bromine is used as an oxidant, a crystalline external phase of β-FeOOH. The high refractive index of some oxidized vermiculites is shown to be due largely to submicroscopic iron oxides.
The eastern end of the Galway granite
Authors: Coats J. S. , Wilson J. R.
Published: December 2006

An account of the eastern part of the Galway Granite is presented together with the first detailed geological map. An aphyric medium-grained alkali granite occurs at the margin of the pluton followed by a coarse porphyritic granite, which becomes more basic towards the granite centre, consistent with findings in the western and northern parts of the batholith. Westwards the coarse porphyritic granite develops a foliation in which xenoliths, and occasionally potash feldspar phenocrysts, are aligned. Chemical fractionation trends illustrate the consanguinity of the granites and aplites. Field, petrographic, and chemical evidence suggest that most of the xenoliths are cognate.

The zonation of the granite is thought to have resulted from crystallization of a magma in which compositional gradients were set up during the early crystallization period. A temperature gradient, decreasing from the centre of the magma chamber outwards into the country rocks, resulted in the migration of water, accompanied by alkalis and other volatiles, towards the granite margin; also the early-crystallizing minerals displaced the residual magma outwards. Crystallization was followed by shearing in the deeper parts of the pluton to produce the granite foliation. A total of 166 rocks have been chemically analysed for 31 constituents.
Feldspars from the Meldon aplite, Devonshire, England
Authors: Nawaz Chaudhry M.
Published: December 2006

Chemical analyses of nine K-feldspars and thirteen albites, along with their optical, physical, and X-ray data are presented. The obliquity values Δ = 12·5(d131-d13¯1) of the K-feldspars are found to be independent of the contents of silica and volatiles in the rocks. The role of temperature as the primary factor affecting the obliquity values is stressed. The relationship between the (An + Ab) content of the potassic phase of K-feldspars and 2Vα is shown diagrammatically.
Microstructures in Cenomanian glauconite from the Isle of Wight, England
Authors: Zumpe Herman H.
Published: December 2006

Cenomanian glauconite grains from the Isle of Wight often possess a thin, pale green shell or ‘corona’ of glauconite. Optical investigation led to recognition of two types of microstructure in these shells; an outer layer with tangentially orientated c-axes, and an inner isotropic layer. A third type of layer with radially orientated c-axes occurs both subjacent to the corona and at lower levels in glauconite grains. This latter occurrence is frequently a relic of a former corona, and indicates two or more periods of glauconite formation. The disposition of the microstructures allows some conclusions to be drawn with respect to the depositional history of individual glauconite grains.
The transformation manganite → pyrolusite
Authors: Champness P. E.
Published: December 2006

During the transformation of manganite to pyrolusite the b-axis must contract about 15 %. There is evidence that the shrinkage takes place partly by contraction of the whole crystal, but electron-microscope investigations of natural pyrolusites and of manganite oxidized in the laboratory show that the reaction also involves the formation of lamellar pores about 85 Å apart, parallel to (010) of the original manganite. Thus, although pyrolusite is tetragonal, the a- and b-axes are not microscopically identical, a fact which could explain why, when natural pyrolusite is treated hydrothermally at 200 and 300 °C and 1000 bars, only one orientation of manganite is formed (Dent Glasser and Smith, 1968). The pores and the accompanying distortion of the structure act as a ‘memory’ of the parent phase.
Pyrophanite from Chvaletice (Bohemia)
Authors: Žák L.
Published: December 2006

Pyrophanite was found in quartz-rhodochrosite veins in hornstones of Algonkian pyritemanganese ores. Photometric reflectance falls from R0 24 and RE′ 19 at 405 mµ to R0 18 and RE′ 15% at 656 mµ (in air). Vickers microhardness (100 g load) demonstrates directional anisotropy, the average value is 611 kg/mm2. Besides the main constituents, subordinate to trace quantities of Mg, Si, Al, Ca, and Cu were recorded by a spectrographic analysis. Unit-cell dimensions are a = 5·131 and c = 14·27 Å. Electron-microprobe analysis gave MnO 43·3, FeO 3·8, MgO 0·05, TiO2 52·9, SiO2 0·1, total 100·15%. The origin of the Chvaletice pyrophanite was most probably connected with a hydrothermal metamorphism of an Alpine-paragenesis type. The source of elements was older sedimentary, basic volcanic, and metamorphic mineral assemblages.
The beryls of the Rosses district, Donegal
Authors: Hall A. , Walsh J. N.
Published: December 2006

Chemical analyses and physical properties are given for six samples of beryl from greisenized granites, pegmatites, and beryl-quartz veins in the Rosses granite complex. The beryls studied were all very similar in composition and contain significant amounts of alkali elements and water in addition to the constituents represented by the formula Be3Al2Si6O18. Calculation of the empirical unit cell contents indicates that most of the H2O+ is present in the mineral as water molecules. The effects of these extra constituents on the physical properties are discussed, and it is suggested that the variation in refractive indices displayed by beryl is to a large extent attributable to the variable water content.
The Sitathali meteorite
Authors: Viswanathan T. V. , Sen Gupta N. R. , Das Gupta D. R. , Banerjee S.
Published: December 2006

Sitathali is an olivine-bronzite chondrite, consisting largely of olivine (Fa18) and orthopyroxene (Fs19) with minor amounts of a clinopyroxene (Ca36Fe12Mg52), plagioclase (An12), nickel-iron, troilite, chromite, and a phosphate (apatite or merrillite). The chemical analysis of a 4 gm sample gave SiO2 39·85, TiO2 0·10, Al2O3 2·84, Cr2O3 0·35, FeO 13·27, MnO 0·28, MgO 23·01, CaO 1·84, Na2O 0·65, K2O 0·15, H2O+ 0·23, H2O− 0·05, P2O5 0·25, FeS 5·09, Fe 10·22, Ni 1·58, Co tr. total 99·76. The metal displays Neumann bands, some deformed, as well as areas of apparent flowage. Troilite locally exhibits twin lamellae and in places replaces kamacite in the plessite fields. Elsewhere it is in braided veinlets and globules, both reflecting former melting. The varied textures suggest a complex post-formational history encompassing several deformational events presumably due to breakups and possible extraterrestrial impacts.
Melting relations of some lavas of Réunion Island, Indian Ocean
Authors: Tilley C. E. , Thompson R. N. , Wadsworth W. J. , Upton B. G. J.
Published: December 2006

The one-atmosphere experimental melting and crystallization relations of some basic lavas of Réunion Island, Indian Ocean, are investigated. They comprise products of the extinct volcano Piton des Neiges and the active volcano Piton de la Fournaise. New data and interpretations are presented for the 1939 oceanite and its contained glass, originally described by Lacroix (1939a). The liquidus v. iron enrichment curves for these Réunion lavas fall about 20 °C above those of the lavas of Kilauea, Hawaii. The primitive liquid reaching the surface contained about 10 % MgO.
Effective molecular weights of the components in solution for the system anorthite-åermanite
Authors: de Wys E. Christiaan , Kapadia Cawas
Published: December 2006

From thermodynamic considerations of the system anorthite-åkermanite it appears that the effective molecular weights of the ‘molecules’ in the melts of this system are 0·5 the molecular weights of anorthite as well as that of åkermanite.

The effective molecular weight value of 0·5 anorthite is in significant contrast to that of 1 anorthite obtained by Adams and Cohen (1966) from a similar analysis of the system anorthite-diopside (Bowen, 1915, and Osborn, 1942). The analysis by Adam and Cohen would lead to a non-ionic silicate melt structure in the system anorthite-diopside in contrast to the accepted electrolytic view of silicate melts. It is suspected that the reason for this apparent difference lies in the published liquidus morphology of the anorthite primary fields of the system anorthite-diopside. This same liquidus morphology is also responsible for the distortions in the isofracts and isotherms in the high-temperature area of the primary field of anorthite of the system anorthite-åkermanite-diopside (de Wys and Foster, 1958).
Shape analysis of moldavites and their impact origin
Authors: Konta J.
Published: December 2006

1666 moldavites from 19 localities in Bohemia and 617 moldavites from 10 localities in Moravia were measured to yield parameters L (length), B (breadth), and T (thickness). A digital computer was programmed to calculate values T/L, (L-B)/(L-T), and according to Sneed and Folk (1958) and values q = B/L, p = T/B, and F = p/q according to Zingg (1935). Averages of large numbers of values characterize Bohemian and Moravian localities. Moldavites from most localities in Bohemia are often drop-like, flat or elongate with average values of between 0·53 and 0·66 and F between 0·68 and 0·91. Moldavites from Moravia are frequently massive to spheroidal with average in the range 0·60 to 0·75 and F between 0·87 and 1·08. Among the localities in Bohemia, four have moldavites with morphological features of Moravian moldavites. The data obtained permit an interpretation that localities of moldavites with low average sphericity contain less heated material. Less heated and thus more viscous glass could have flown along shorter trajectories (Bohemia). More heated glass was ejected to geographically more distant places (Moravia) or travelled along relatively long steeper trajectories (several localities in Bohemia).
Mineral reactions at a peridotite-gneiss contact, Jotunheimen, Norway
Authors: Griffin W. L.
Published: December 2006

The assemblage aluminous pyroxenes+ spinel forms reaction zones between olivine-rich and plagioclase-rich layers in the Jotunheimen complex. These zones have probably formed by cooling from high T at moderate P, passing through the ol + plag → pyroxenes + spinel reaction. The absence of garnet, which would be expected to form upon further cooling, is attributed to interruption of the cooling history by rapid uplift. This uplift is demonstrated by symplectitic breakdown of aluminous pyroxenes, with expulsion of Ts and Acm, to yield low-Al pyroxenes, spinel, and plagioclase. The uplift must be Precambrian, and suggests that the Jotun rocks were involved in rapid vertical movements long before the Caledonian thrusting took place.
A precise and accurate method for the quantitative determination of carbonate minerals by X-Ray diffraction using a spiking technique
Authors: Gunatilaka H. A. , Till Roger
Published: December 2006

A precise and accurate X-ray diffraction method has been developed whereby the weight percentages of aragonite and low- and high-magnesium calcite are determined from the integrated peak areas of spiked and unspiked samples. The spike mixture was prepared from organisms extracted from the samples to be analysed. Use of a spiking method also avoided the preparation of working curves from artificial mixtures of carbonate minerals, which may not have the same diffraction behaviour as the unknowns. A test of the precision of the method indicates the following coefficients of variation: aragonite, 1·4 %; low-magnesium calcite, 1·5 %; high-magnesium calcite, 7·8 %. A test of the accuracy of the method indicates no significant bias in any of the carbonate results, except in samples where high-magnesium calcite values are below 10 %. Quartz may also be determined by this method (coefficient of variation 23·9 %; positive bias in values greater than 10 %).
A new occurrence of vanadium minerals in Leicestershire
Authors: King Robert J. , Dixon John A.
Published: December 2006

Two vanadates, tangeïte and volborthite, new to Britain, their association with vanadiferous nodules, and their geological environment are described. A percentage composition graph for vanadium taken across a vanadiferous nodule, by scanning electron probe, is given.
Zapatalite, a new mineral from Sonora, Mexico
Authors: Williams Sidney A.
Published: December 2006

Zapatalite, Cu3Al4(PO4)3(OH)9·4H2O, was first found at a small prospect north-west of Cerro Morita, 27 kilometers south-west of Agua Prieta, Sonora. It occurs in silicified and brecciated limestone with libethenite, chenevixite, beaverite, alunite, and pseudomalachite.

Zapatalite is pale (faience) blue with pale blue streak; H = 1½, G = 3·016±0·026. It is soluble in cold dilute acids and decomposed by 20% KOH. Duplicate analyses on samples of about 9 and 15 mg gave CuO 27·92, 25·77%; Al2O3 20·16, 20·26%; P2O5 20·69, 22·51%; H2O 15·46, 15·79%; insol. (baryte and quartz), 15·46, 15·79%. This leads to the formula Cu3Al4(PO4)3(OH)9·4H2O.

The cell can be indexed as tetragonal with a 15·22Å, c 11·52Å, and a volume of 2669Å3. If Z = 6, empirical cell contents are Cu19·4Al22·8(PO4)17·6(OH)55·422·2H2O, and the calculated G = 3·017. Strongest lines of the powder pattern are 7·62 (10), 11·60 (10), 5·75 (7), 6·82 (7), 3·04 (5), 2·53 (5), 2·95 (4), and 2·88 (4).

Pale green in thin section with feeble dichroism in green, with ε > ω. The good basal cleavage is a length slow direction. Indices for Na-D are ε = 1·635, ω = 1·646. Usually uniaxial (—), but may be biaxial (—) with variable 2 V.

Named for Emiliano Zapata (1879–1919), a popular hero of the Mexican revolution. Type specimens to be left with British Museum (Natural History) and the University of Arizona.
Jacob Forster (1739–1806) and his connections with forsterite and palladium
Authors: Frondel Clifford
Published: December 2006

The person after whom forsterite was named has been confirmed as Jacob Forster (1739–1806), a mineral collector and dealer of London. The discovery of palladium and rhodium by William Hyde Wollaston and of iridium and osmium by Smithson Tennant appears to have been made on crude platinum ore from South America supplied by Forster.
The crystal structure of dundasite
Authors: Cocco G. , Fanfani L , Nunzi A. , Zanazzi P. F.
Published: December 2006

The crystal structure of dundasite from Gonnesa (Italy) was solved by a three-dimensional Patterson function computed using intensity data collected photographically by the Weissenberg method, and refined by successive Fourier maps and least-squares cycles to an R index 0·.066 for 505 independent observed reflections.

The chemical formula resulting from the structural analysis is PbAl2(CO3)2(OH)4·H2O. The mineral is orthorhombic, space group Pbnm, with a 9·08 Å, b 16·37 Å, c 5·62 Å. The dundasite structure consists of a three-dimensional framework of coordination polyhedra around Pb and Al. Pb ions are coordinated by nine oxygen atoms with distances ranging from 2·53 to 2·91 Å. Al ions show the usual octahedral coordination with average Al-O distance 1.90 Å. C-O mean distances are 1·28 and 1·27 Å for the two non-equivalent CO3 groups. The water molecules are not coordinated by the cations.
Garnetiferous striped amphibolites from
Connemara, Western Ireland
Authors: Leake Bernard E.
Published: December 2006

The chemical factors controlling the rare
appearance of garnet in Connemara amphibolites are
elucidated, including the importance of low
oxidation ratio (w), low Mg/(Mg+Fe+Mn) (mg), and
high MnO. Pressure is believed to be critical in
determining whether garnet is common in
amphibolites in any one terrain and it is
suggested that the ratio mg × w/MnO (called g) in
serial analyses of garnetiferous amphibolites can
be used as a measure of the pressure of
metamorphism.

89 Connemara amphibolite analyses with
plagioclase and hornblende are considered
including 31 new analyses, which are reported. Of
the 89 analyses, 10 contain garnet, 6
cummingtonite, 16 clinopyroxene including 3 with
garnet and clinopyroxene and 2 with garnet and
cummingtonite. The coexisting garnet and
hornblende in 3 amphibolites have been analysed,
including one sample in which brown-green and
green hornblende, cummingtonite, plagioclase,
garnet, and ilmenite have been analysed.
Cummingtonite does not coexist with clinopyroxene
or sphene and its presence is controlled by
pancity of Ca as well as medium to low pressure in
metamorphism.
Plagioclase-Ca-rich-nepheline intergrowths
in a syenite from the Marangudzi complex,
Rhodesia
Authors: Henderson C. M. B. , Gibb F. G. F.
Published: December 2006

Nepheline in a basic syenite from the
Marangudzi complex is relatively Ca-rich with CaO
from 1·9 to 2·4 (wt) %. This Ca-rich nepheline
sometimes occurs in intimate intergrowths with
plagioclase (andesine). These intergrowths are
thought to have formed at temperatures in the
order of 750°–850°C by resorption of plagioclase
with simultaneous replacement by
nepheline.
Trace element geochemistry of parts of the Closepet granite, Mysore State, India
Authors: Rao V. Divakara , Aswathanarayana U. , Qureshy M. N.
Published: December 2006

Trace elements in twenty samples of the Closepet granite (grey and pink varieties) and the related rocks have been determined by neutron activation analysis (Th, Rb, and Cs), fluorometry (U), flame-photometry (K), and emission spectroscopy (Pb, Sr). The trace element contents of the grey and pink varieties are generally similar. An analysis of the magnitudes of the trace element and other ratios (K/Rb, 235; Th/U, 6·4; U/K (× 104), 0·7; K/Cs (× 10−4), 3·6; Th/K (× 104), 5·3; Fe2O3/(FeO+Fe2O3), 0·27) as well as87Sr/86Sr initial ratio (0·705; Crawford, 1969) of the Closepet granite indicate two possible modes of genesis: Either the granite magma was not highly differentiated and the vapour phase was relatively insignificant; the crystallization of the magma took place under essentially non-oxidizing conditions; the pink variety, which followed the grey variety, crystallized under essentially the same conditions as the grey variety. Or the Closepet granite had a two-stage history—palingenesis (starting from the Peninsular gneiss) and metasomatism involving the enrichment in K, Rb, Pb, and Th and depletion of Sr and Cs, among others.
An interpretation of the hydroxyl contents
of biotites and muscovites
Authors: Forbes Warren C.
Published: December 2006

The net cationic charge of the octahedral
and tetrahedral layers was calculated from the
analyses of 100 biotites and 93 muscovites and
compared to the observed hydroxyl contents
(OH+F+Cl). The correlation coefficient between
these parameters of −0·96 for biotites and −0·82
for muscovites demonstrates that the hydroxyl
content in these micas varies in response to
cationic substitutions. Thus substitutions in
micas involve cation-hydroxyl replacement couples
in addition to other modes previously recognized.
Tetrasilicic phlogopite,
K2Mg6Si8O22(OH)2,
which is related to phlogopite by the substitution
Al3+ +
H+ =
Si4+ was synthesized but is
not a stable phase under the conditions
investigated. This mica crystallizes as a 1M
polymorph with a =
5·289(2) Å, b =
9·151(3) Å, c =
10·247(3) Å, β =
100°4(2).

Exchange reactions, such as
Al3+ +
H+ ⇌
Si4+, between phlogopite and
pyroxenes at depth may provide a mechanism for
release of H+ within the
mantle.
A chromian tourmaline from Swat, West
Pakistan
Authors: Jan M. Qasim , Kempe D. R. C. , Symes R. F.
Published: December 2006

Traces of a green chromian tourmaline
occur in calcareous rocks in contact with
serpentinite near Alpurai, Swat, West Pakistan.
The petrography of the rocks and the optical
properties of the tourmaline are presented along
with its chemistry (it contains over 8 %
Cr2O3
and about 0·2 %
V2O3).
The mineral is compared with other chromian
tourmalines and its paragenesis discussed: it is
thought to have been produced by silica-rich
hydrothermal (or gaseous) solutions, which have
crystallized as thin quartz veins in the
calcareous rocks, introducing boron and other
constituents.
Embreyite, a new mineral from Berezov, Siberia
Authors: Williams S. A.
Published: December 2006

Embreyite is a new mineral that has been found only in old specimens collected at Berezov, Siberia. The composition is Pb4·97(CrO4)2·00(PO4)1·91.0·75H2O, or Pb5(CrO4)2(PO4)2. H2O based on both wet and electron-probe analyses. Z = I, Dmeas 6·45, Deale 6·41. Crystals are monoclinic with a 9·755 Å, b 5·636, c 7·135, β 103°5′ the space group may be P21/m. No single crystals were found. α = 2·20, β = γ = 2·36. Colour in various shades of orange with a yellow streak. H = 3½; no cleavages observed. Occurs with vauquelinite, crocoite, and phoenicochroite in the oxide zone assemblage from Berezov.
Metasomatized (fenitized) quartzites from the Borralan Complex, Scotland
Authors: Woolley A. R. , Symes R. F. , Elliott C. J.
Published: December 2006

Fenitized quartzites are described from three localities around the Borralan alkaline igneous complex. Chemical and electron-probe analyses of amphiboles, pyroxenes, micas, and feldspars are given. Early-formed amphiboles are calcic, but these are replaced by alkaline varieties with increasing fenitization. Rock analyses indicate a ‘straight line’ rate of increase of Ti, Fe2+ + Fe3+, Mg, Al, K, and a more variable increase of Ca and Na atoms, at the expense of Si atoms. The simple composition of the unaltered quartzite allows the accurate calculation of bulk changes during fenitization. The final product of the alkali metasomatism is a syenite lying close to the albite-orthoclase minimum though the primary source of the fenitizing fluids was probably a highly potassic magma.
Talc-kyanite-quartz schists and other high-pressure assemblages from Zambia
Authors: Vrána S. , Barr M. W. C.
Published: December 2006

Talc-kyanite-quartz schists, Mg-chlorite-kyanite-quartz schists, kyanite gedritites, and kyanite-bronzite gedritites occur in the Central Province of Zambia. Experimental work in the system MgO-Al2O3-SiO2-H2O suggests that these assemblages formed at pressures in excess of 10 kb.
New data on the composition of Caledonian granites
Authors: Hall A.
Published: December 2006

New analyses are given of granites from 23 intrusions in Scotland, Ireland, and the Isle of Man. Together with existing analyses, these were used to measure the regional variation in composition of Caledonian granites by means of trend surface analysis. An explanation of the variation is presented that involves the production of magma by melting in the crust, at a depth determined by the geothermal gradient.
X-Ray data and chemical analyses of some titanomagnetite and ilmenite samples from the Bushveld Complex, South Africa
Authors: Molyneux T. C.
Published: December 2006

The cell dimensions of powder samples of some Bushveld titanomagnetites and ilmenites were determined using a 114·6 mm AEG Guinier camera. The average cell dimension of the titanomagnetite is 8·400±0·005 Å and there is no definite relationship between the cell edge of the samples and their position in the layered sequence. The average cell parameters of coarse-grained ilmenite are a 5·085±0·005 Å and c 14·09±0·02 Å. Ilmenite that has replaced ulvöspinel has on average a value of some 0·003 Å greater than that of associated coarse ilmenite grains.

Chemical analyses indicate that titanomagnetite from pegmatoidal plugs and from the top of layered sequence was generally subject to late-stage magmatic alteration and hence lies in the Titanomagnetite II field. In the Bushveld Complex there is an increase in the TiO2 content of titanomagnetite from some 12 % at the base to 18 % at the top of the Upper Zone. However, Bushveld titanomagnetite tends to be poorer in TiO2 than similar samples from the Skaergaard intrusion.

A discrepancy between modal and normative hercynite in the Bushveld samples indicates that a considerable amount of hercynite is probably still in solid solution in the titanomagnetite.

Chemical analyses of Bushveld ilmenites reveal that they lie in the same tholeiitic field as those of the Skaergaard intrusion.
The decomposition and analysis of chrome spinel. A survey of some published techniques
Authors: Rodgers K. A.
Published: December 2006

Examination of published procedures for the decomposition and subsequent analysis of chromite and chrome ores shows some to be unnecessarily complicated and time consuming. Others fail to yield consistent and reproducible results. Decomposition is rapidly and effectively accomplished using the peroxide frit technique of Rafter. Chromium may then be removed and determined volumetrically allowing the rest of the analysis to proceed along conventional silicate lines. Fe2+ is determined by oxidimetry following digestion with a mixture of phosphoric and sulphuric acids in the presence of ceric sulphate.
Calculation of crystal field splittings in
distorted coordination polyhedra: spectra and
thermodynamic properties of minerals
Authors: Wood Bernard J. , Strens R. G. J.
Published: December 2006

A simple method has been developed for
calculating the
d-orbital energy levels
of transition-metal ions in coordination polyhedra
with both orthogonal and non-orthogonal
distortions, using equations based on those
derived by Ballhausen (1954). The input data are
atomic coordinates, a standard value of the
crystal field splitting parameter Δ at known
metal-ligand distance, and the ratio of radial
integrals
B2/B4,
which is approximately constant for a given ion.
The method can be applied to polyhedra containing
different ligands.

Application of the equations to the
Mn3+
(M3) site in piemontite
and the Fe2+
(M2) site in
orthopyroxene gives calculated transition energies
in good agreement with the observed band
energies.

The calculations permit definite
assignment of the great majority of
d-d absorption bands
even in multi-site phases, and enable
discrimination of crystal-field and
charge-transfer bands in mineral spectra. They
also throw light on the fine structures of both
oxygen → metal and metal → metal charge-transfer
bands, and allow the calculation of crystal-field
stabilization enthalpy and electronic entropy. The
latter is a previously neglected energy term that
contributes significantly to the energetics of
reactions within and between phases containing
transition-metal ions.
Melilite crystallization in the system
CaO-MgO-Al2O3-SiO2
Authors: Biggar G. M. , O'Hara M. J.
Published: December 2006

The solidus temperatures (IPTS-68) and
melilite compositions (mole %) determined for some
four-phase assemblages in the system
CaO-MgO-Al2O3-SiO2
are: anorthite, diopside, spinel melilite
(Åk81Geh19),
1236·5 °C; diopside, spinel, forsterite, melilite
(Åk83Geh17),
1238 °C; foresterite, spinel, monticellite,
melilite
(Åk82Geh18),
1351 °C; monticellite, merwinite, spinel, melilite
(Åk52Geh48),
1378 °C; dicalcium-silicate,
Ca5MgSi3O12,
spinel, melilite
(Åk5Geh95),
ca. 1412 °C; dicalcium-silicate,
Ca6MgAl8SiO21,
spinel, melilite
(Åk4Geh96),
ca. 1347 °C.
Computer simulation of cation distribution
in the octahedral layers of micas
Authors: Krzanowski W. J. , Newman A. C. D.
Published: December 2006

Without direct evidence that cations
favour particular sites in the octahedral layers
of phlogopite-biotite micas, it is usually assumed
that the cations are distributed randomly. Such a
distribution, however, implies appreciable
populations of cation combinations that seem
electrostatically improbable. A computer program
was written that rearranges a random distribution
so that the improbable combinations of cations are
eliminated by predetermined restrictions. Its use
shows that conditions deduced from Pauling's
electrostatic valence rule lead to grouping of
trivalent cations around vacancies; for some
chemical compositions, chains of alternate
trivalent cations and vacancies extend through the
structure.
Some chemical data on members of the
shoshonite association
Authors: Joplin Germaine A. , Kiss E. , Ware N. G. , Widdowson Jennifer R.
Published: December 2006

A number of minerals and residual glasses
from absarokites, shoshonites, and latites have
been analysed by electron probe.

Clinopyroxenes show very little
iron-enrichment and these rocks are thus
distinguished from tholeiites and alkali
basalts.

Glasses from this group are also distinct
from tholeiites and alkali basalts and occupy a
separate field on a
CaO-Na2O-K2O
diagram.
Spinels from the Dawros Peridotite,
Connemara, Ireland
Authors: Rothstein A. T. V.
Published: December 2006

Two different spinels, analyses of which
are given, occur in the layered ultramafic rocks
at Dawros. Chrome spinel occurs both as
gravity-stratified cumulates and as complex orbs,
while an Al-rich spinel is both in rocks of the
main Dawros magmatic sequence and in an
association with an aluminous bronzite, which may
originate by recrystallization. It is concluded
that while the chrome spinel is certainly of
magmatic origin, the aluminous spinel is probably
partly of magmatic and partly of recrystallization
origin.
Aguilarite from the Camoola Reef, Maratoto
Valley, New Zealand
Authors: Main J. V. , Rodgers K. A. , Kobe H. W. , Woods C. P.
Published: December 2006

Aguilarite, Ag4SeS,
occurs in a hydrothermal vein deposit associated
with sphalerite, chalcopyrite, galena, and native
silver. Physical and chemical data agree with
descriptions from Guanajuato (type locality).
Differential thermal analysis of synthetic
material indicates an inversion temperature of
122±1 °C. The mineral crystallized late in the
paragenetic sequence, probably slightly above 200
°C.
Stressed pyroxenite nodules from the Jagersfontein kimberlite
Authors: Borley G. D. , Suddaby P.
Published: December 2006

Examination of some pyroxenite nodules from the Jagersfontein kimberlite shows that they have suffered variable deformation followed by different degrees of recovery. Most interes~ting of the nodules is the 'diallage rock', which consists of highly sheared and broken lamellar crystals of diopside containing exsolved enstatite. Petrographic evidence indicates a pre-tectonic exsolution of enstatite and a syntectonic exsolution of pyrope-almandine from enstatite. Deformation occurred in the mantle, prior to incorporation of the nodule in the kimberlite. Compositions of pyroxenes from the diallage rock suggest it re-equilibrated at a temperature of 1000° and at a pressure of about 35 kb. Olivine and phlogopite, accompanied by serpentine, occur only in broken kink-bands in the diallage rock and they are considered to be of secondary origin, precipitated from kimberlite magma at temperatures near 700°
Lower Tertiary Tholeiitic Basalts from Southern New Caledonia
Authors: Rodgers K. A.
Published: December 2006

Eocene tholeiitic basalts occur throughout the length of New Caledonia where their emplacement preceded that of the peridotite massifs. In the south, two areas of basaltic rocks are intimately associated with Eocene sediments, which have been overridden by the peridotites. The aphyric, holocrystalline basalts consist of plagioclase, clinopyroxene, titanomagnetite, and minor quartz together with their abundant alteration products, which include epidote and uralite. The chemical compositions of these rocks fail to show agreement with oceanic tholeiitites, as suggested by earlier writers, although strong similarities exist with the basalts of the Papuan Ultramafic Belt.
Identification of iron-containing impurities in natural kaolinites using the Mössbauer effect
Authors: Hogg C. S. , Malden P. J. , Meads R. E.
Published: December 2006

Two clay samples originating in the kaolinized granite area near St. Austell, Cornwall, have been examined by Mössbauer spectroscopy. The iron-containing impurity in the sample with a red discoloration (sample A) has, by measurement of the hyperfine magnetic field, been identified as hematite. In the case of sample B, which was yellow in colour, preliminary Mössbauer work indicated β-FeOOH as the impurity, but detailed measurements of hyperfine field and Nöel temperature, when compared with similar results for a synthetic β-FeOOH sample, suggested otherwise. X-ray and chemical work suggested that the iron-containing phase in sample B is goethite, α-FeOOH in which some substitution of Al+3 for Fe3+ has occurred; the Mössbauer data are consistent with this conclusion. Both clay samples exhibited superparamagnetic behaviour and this has been utilized to obtain rough estimates of the mean radius of the particles of the iron-containing impurity. These were 117 Å for the α-Fe2O3 in sample A and 270 Å for aluminian α-FeOOH in sample B.
Carlfriesite, H4Ca(TeO3)3, a new mineral from Moctezuma, Sonora, Mexico
Authors: Williams Sidney A. , Gaines Richard V.
Published: December 2006

Carlfriesite is a new species found in relative abundance at the Bambollita (now La Oriental) mine in the Sierra La Huerta near Moctezuma, Sonora. Colour primrose yellow (R.H.S. 4B) with pale yellow streak. H = 3½, Dmeas = 6·3, Dcalc = 5·93. Fair cleavage on {010}. Monoclinic with a 12·585 Å, b 5·658, c 9·985, β 115° 35′. Space group Cc or C2/c. Strongest lines are 3·167 (10), 3·082 (9B), 5·063 (6), 2.832 (6), 3·369 (4), 4·825 (3), 2·698 (3), and 4·o89 (2). Feeble pleochlroism in pale yellow with γ > α = β α = 1·982, β = 2·095, γ 2·19 2Vα, = 79° calc. Occurs with cerussite and chlorargyrite in an oxidized assemblage derived from hessite, galena, and bornite.
The crystal structure of schairerite and its relationship to sulphohalite
Authors: Fanfani L. , Nunzi A. , Zanazzi P. F. , Zanzari A. R. , Sabelli C.
Published: December 2006

The crystal structure of schairerite from Searles Lake, California, has been determined employing X-ray diffraction data collected on a single-crystal diffractometer. The crystal structure was refined by least-squares methods employing isotropic thermal parameters to a final R index of 0·07 for 2536 independent observed reflections. The cell content is 3[Na21(SO4)7F6Cl]. The space group is P31m with a 12·197 A and c 19·259 Å. Schairerite exhibits a marked sub-cell (a 7·042 Å, the same c axis and P3m1 symmetry), which may be related to the unit cell of sulphohalite when described in a hexagonal lattice.

The crystal structure of schairerite may be considered as consisting of seven sheets of Na+ ions perpendicular to the c axis. These sheets are connected to each other .building up a three-dimensional framework. The Na+ ions in these sheets are arranged in an array built up of hexagons and triangles. Sulphur atoms lie in the sheets at the centres of each hexagon, the halogen atoms lying between the sheets midway between the centres of two triangles. A comparison with sulphohalite shows that the close lattice analogies may be related to a similar atomic arrangement. Apart from the differences in chemical formula (F:C1 ratio 1:1 in sulphohalite), the main difference in the structural framework consists of the unequal number of Na+ sheets (six in sulphohalite) and in the SO42− tetrahedra orientation.
Nickel-containing montmorillonites and chlorites from Brazil, with remarks on schuchardtite
Authors: Brindley G. W. , De Souza Jefferson V.
Published: December 2006

Clay-like, hydrous nickel silicates from Niquelandia, Goias, Brazil, and from Jacupiranga, São Paulo, Brazil, arc examined by X-ray diffraction, chemical analysis, and thermogravimetric methods. The nickel silicates from Niquelandia are ferric iron montmorillonites, with nickel in the octahedral positions and, to a lesser extent, in interlayer positions. The chemical compositions of samples dried at 110°C average (Mg0.15Ni0.08Ca0.015Na0.005) (Fe0.92IIIFe0.025IIAl0.55Mg0.37Ni0.22) (Si3.88Al0.12)O10(OH)2(H2O)0.93. The layer charge originates largely in the octahedral sheet. The cation-exchange capacities average 107 me/100 g clay (110°C). These minerals differ from non-tronites, in which the layer charge originates mainly in the tetrahedral sheets.

The nickel silicates from Jacupiranga resemble chlorites, with a non-expanding basal spacing of 14·2-14·3 Å. The better crystalline forms give X-ray data in good agreement with a la polytype structure, which is consistent with their formation by low-temperature processes. Chemical formulae derived on the basis of O10(OH)8 give an average of 5·47 cations in octahedral positions. Thermogravimetric measurements show up to 4% H2O lost between 110 and 500 °C. These results suggest a partial vermiculitization of the interlayer sheets. A new method of calculating a structural formula is developed that gives an interlayer composition of the form R1.75(OH)3.75(H2O)1.14, with (OH + H2O)/R = 2·80, which approaches the ratio for a dioctahedral sheet structure.

A comparison of these defect chlorites with available data on schuchardtites shows many similarities; however, schuchardtite is not yet sufficiently well denned for the Jacupiranga chlorites to be given this name.
Chemical variation among French ultramafic xenoliths—evidence for a heterogeneous upper mantle
Authors: Hutchison R. , Chambers A. L. , Paul D. K. , Harris P. G.
Published: December 2006

Some 200 ultramafic xenoliths and their basaltic hosts from five French localities were studied. New analyses are presented, which show the five host-rocks to be nepheline- and olivine-normative. Seven bulk analyses of xenoliths from four localities, together with analyses of their constituent diopsides and, for six, of their orthopyroxenes, are also presented. Xenoliths from four occurrences appear to have equilibrated at pressures between about 8 to 18 kb at sub-basaltic solidus temperatures. Suites of xenoliths are chemically different. Histograms were used to determine compositions of depleted and ‘undepleted’ upper mantle. A suite of peridotite xenoliths from the Bult-fontein kimberlite pipe is no less depleted in fusible oxides than xenoliths from two French localities. ‘Undepleted’ upper mantle is very similar to ‘pyrolite’ in composition, except that the latter has much higher TiO2, Na2O, and K2O contents. No xenolith encountered in this work has a bulk composition that could yield more than 12% oceanic tholeiite on partial melting.
Anorthosite—first occurrence in Nigeria and relevance to Younger Granite genesis
Authors: Wright J. B.
Published: December 2006

Plagioclase crystal fragments and a block of anorthosite occur in small basaltic dykes on the Jos Plateau. The anorthosite is unusual, for the feldspar is labradoritic, but the interstitial mineralogy is granitic rather than basic, displaying granophyric intergrowths in places. The anorthosite is probably not an intermediate stage in fractionation from a basic parent magma towards granite, since over 95 % of this large province is granitic and the volume of basic magma required would be prohibitively large. Nor did it develop as an intermediate stage in fractionation from a salic parent magma, e.g. syenite, because the plagioclase is too calcic to have crystallized from a syenitic melt. Basic to intermediate dykes are numerous though volumetrically insignificant in the Younger Granite province. The anorthosite may be related to the evolution of small volumes of basaltic magma, which had little to do with Younger Granite magmatism.