Topaz, so common an accessory in tin lodes in all parts of the world, has hitherto been looked upon as comparatively rare in Cornwall. When massive, or even in the form of small, well-developed crystals, it is a mineral easily overlooked, or apt cursorily to be mistakcn for quartz.

The presence of topaz as a microscopic accessory in granite, greisen, and rarely elvans, from most of the Cornish masses, has been determined by Dr. J. S. Flett in the course of the work of the Geological Survey; while the late Mr. J. H. Collins was responsible for the record of other interesting localities.

In the present notes I have collected all the available information respecting its mode of occurrence and localities ; and have added several new ones, at some of which the mineral occurs in considerable mass, thus affording evidence that topaz is in Cornwall, as in the case of other countries, a comparatively common associate of cassiterite and wolframite, both in granite and sedimentary rocks.

In a recent number of this Magazine (1897, XI. p. 192) a paper by me on "The Crystallography of Plagionite" gives the results of goniometric measurements and specific gravity determinations made on crystals of plagionite from Wolfsberg in the Harz; it was also suggested on crystallographic grounds that the mineral from Arnsberg in Westphalia described by Pisani as heteromorphite was identical with plagionite: but as no quantitative chemical analyses were made on the material measured, these results were not altogether satisfactory.

Ganophyllite has been shown to have alkali cation exchange capability. Partial cesium exchange for K + Na in large (> 0·3 mm) grains shows that the exchangeable cations migrate parallel to X, the crystallographic direction for the ‘interlayer’ tunnels. Such exchange capability supports the suggestion that the alkali elements are located in zeolite-like sites attached to the sides of the tunnels. Exchange experiments show that complete sodium substitution for potassium is possible also. Eggletonite, the Na analogue of ganophyllite, is shown to have an identical superlattice to ganophyllite, indicating that eggletonite differs from ganophyllite only by the exchangeable cation.

Thin sections afford a very inadequate basis for the determimation of thc accessory minerals present in the Dartmoor granite, and they are of little or no value for assessing the relative proportions of these minerals. A recognizable cryst'd of zircon, for example, is rarely seen iu thin sections of this granite, and uutil zircons were isolated in quantity from the crushed rock, stream-sands, &c., one type of zircon was not detected.

Leucite and pseudoleucite invariably have lower K/Rb ratios and higher K/Sr and K/Ba ratios than the groundmasses of the rocks in which they occur. The distribution of Rb, Sr, and Ba between K-rich minerals (e.g. alkali feldspars) and the liquids from which they crystallize is generally such that Rb is impoverished and Sr and Ba enriched, relative to K, in the crystallizing phase. Leucite shows the opposite relationship and this is attributed to the leucite structure being sensitive to the size and valency of the ions replacing K.

Previous work by Donnay on the basis of the geometrical theory of twinning related the width of albite twin lamellae to the composition of the plagioclase. The curve derived by Donnay has been recalculated for both high- and low-temperature felspars from X-ray data; the two curves differ markedly in the region between 0 and 20 % An. Some experimental evidence in support of the deductions that can be made is given.

Experiments have been conducted to determine the optimum conditions for the hydrothermal growth of ruby. The solubility of corundmn in various solutions has been determined and compared with the respective growth obtained in each medium. The discrepancy between solubility and effective growth is discussed.

The need for a high degree of chemical purity has resulted in the development of platinum liners for the autoclaves. The effects of impurities and of other factors on the growth of ruby crystals have been studied. The crystal habit of hydrothermal ruby is also described.

The object of this paper is to demonstrate the widespread occurrence of zoned olivines in igneous rocks, to show that the zoning is continuous, that the composition varies from a magnesium-rich centre to an iron-enriched margin, and that these findings have an important bearing on the question of petrogenesis.

I propose to express the composition of olivine by stating only the percentage of fayalite, as the rock-forming olivines belong mainly to the forsterite-fayalite series. There are, however, a number of names in use for the members of this series. Assuming that the two names forsterite and fayalite are insufficient for the needs of classification, it yet seems to me that all but four of the existing names are superfluous.

In a recent paper (hereafter referred to as GD) Goodyear and Dufiln (1954) described X-ray powder data for a number of synthetic and chemically analysed plagioclases of composition An0Abl00-Anl00Ab0. Important aspects of this work were a correlation of the X-ray patterns with chemical composition, and a distinction between the pattern of a naturally occurring material of low-temperature origin and that of a synthetic of similar composition. The investigation showed quite clearly that the unit-cell dimensions of a synthetic plagioelase depend but little on composition from An0Abl00 to An70Ab30, whilst they differ from those of the low-temperature modification greatly for albite, to a lessening degree as the composition approaches An70Ab30, and practically not at all in the range An70Ab30-Anl00Ab0.

Gatehouseite is a new manganese hydroxy phosphate from Iron Monarch, South Australia. The new mineral occurs as radiating clusters of pale yellow, and yellow to pale brownish orange bladed crystals up to 100 ~tm in length. The crystals are elongated along [010] and the principal forms are {102}, {110} and {001}. Gatehouseite also occurs as overgrowths on prismatic arsenoclasite crystals. Associated with gatehouseite are baryte, shigaite, manganoan ferroan calcite, hausmannite and hematite. Gatehouseite appears to have formed at low temperature by the interaction of phosphorus-rich fluids on hausmannite in carbonate-rich fractures in the hematite ore. Electron microprobe analysis yielded: MnO 64.42, FeO 0.19, CuO 0.03, ZnO 0.03, PbO 0.05, Al2O3 0.10, P2O5 22.18, V2O5 0.38, As2O5 3.58, H2O (6.44%). These data gave an empirical formula of Mn5.09Fe0.01Al0.01(P1.75As0.17-V0.02)∑1.94O8(OH)4.00, calculated on the basis of 12 oxygen atoms. The simplified formula is Mn5(PO4)2(OH)4. The mineral is transparent with a pale yellow streak, an adamantine lustre and an estimated Mohs hardness of 4. The crystals exhibit a distinct cleavage on {010} and have a splintery fracture. The strongest lines in the X-ray powder pattern are (dobs, Iobs, hkl) 4.48 (10) (004); 4.03 (10) (104); 2.900 (100) (11.5); 2.853 (70) (106); 2.801 (50) (021); 2.702 (80) (303); 2.022 (15) (322); 1.608(15) (330). These data were indexed on an orthorhombic cell, with a = 9.097(2), b = 5.693(2), c = 18.002(10) Å and a volume of 932.4(8) Å3; the space group is probably P212121. For Z = 4 and using the empirical formula, the calculated density is 3.74 g/cm3. Optical properties could not be determined in full; two refractive indices are 1.74(1) and 1.76(1) (white light); pleochroism is distinct from brown to near colourless. The crystals are length slow with parallel extinction. The name is for Dr. Bryan Michael Kenneth Cummings Gatehouse (1932-), crystal chemist of Monash University, Melbourne, Australia.

Paratooite-(La) is a new lanthanum-dominant rare-earth copper carbonate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Paratooite-(La) occurs as sheaves and radiating sprays of blade-like to tabular pale blue crystals in thin fissures in a slaty country rock. Individual crystals are typically 50–200 μm in maximum dimension but <5 μm thick. Associated minerals include donnayite-(Y), kamphaugite-(Y), and bastnäsite-(La). Electron microprobe and CHN analyses gave: La2O3 26.47; Pr2O3 7.74; Nd2O3 8.15; Sm2O3 0.66; Gd2O3 0.85; Y2O3 0.72; CaO 7.57; SrO 3.15; Na2O 3.3; CuO 5.77; F 0.24; CO2 32.05; NO2 1.12; -O=F -0.10; sum 100.03, yielding an empirical formula of (La3.54Ca2.94Na2.32Nd1.05Pr1.03Sr0.66Y0.14Gd0.10Sm0.08)Σ11.86Cu1.58(C15.84N0.53)O47.76F0.24. The simplified formula is (REE ,Ca,Na,Sr)6Cu(CO3)8 or possibly REE3(Ca,Sr)2NaCu(CO3)8. The mineral is pale turquoise-blue to pale blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology and TEM studies indicate a cleavage parallel to ﹛100﹜. The Mohs hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl )]: 5.047 (53) (200); 4.786 (49) (021); 3.957 (43) (220); 3.468 (43) (012, 221); 2.927 (100) (202); 2.530 (52) (241); 2.344 (22) (420,103); 2.232 (20) (421). A synchrotron powder diffraction pattern was indexed on a primitive orthorhombic cell with a = 10.0862(5), b = 12.8088(6), c = 7.2360(4) Å, V= 934.8(1) Å3 and Z = 2. The crystal structure of the new mineral could not be determined but powder diffraction data indicate the space group is probably P 222, Pmmm , P 2221 or Pmm2. The measured density is 3.68(3) g/cm3 and the calculated density is 3.78 g/cm3. Paratooite-(La) is biaxial negative with α = 1.605(3), β = 1.696(3) and γ = 1.752(2); pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint) with absorption Z ≈ Y >> X. Paratooite-(La) is a supergene mineral which precipitated from mildly basic carbonated groundwaters. The mineral is named for the type locality.

Munakataite, Pb2Cu2(Se4+O3)(SO4)(OH)4, has been found in association with a variety of rare secondary Te minerals at Otto Mountain, San Bernardino County, California, USA. It is very rare and occurs as subparallel bundles of blue needles up to 1 mm long. Electron microprobe analyses provided the empirical formula Pb1.96Cu1.60[(Se0.894+S0.11)∑1O3](SO4)[(OH)3.34(H2O)0.66]∑4- Munakataite is mono-clinic, space group P21/m, with cell parameters a = 9.8023(26), b = 5.6751(14), c = 9.2811(25) Å, β = 102.443(6), V = 504.2(2) Å3 and Z = 2. The crystal structure, solved by direct methods and refined to R1 = 0.0308 for 544 Fo > 4σF reflections, consists of Jahn-Teller-distorted Cu2+O6 square bipyramids. which form chains along b by sharing trans edges across their square planes. The chains are decorated by SO4 tetrahedra and Se4+O3 pyramids, which bond to apical corners of adjacent bipyramids. The chains are linked to one another via bonds to two different PbO9 polyhedra, only one of which exhibits one-sided coordination typical of Pb2+ with a stereochemically active 6s2 lone-electron-pair. Munakataite is isostructural with schmiederite and the structure is closely related to that of linarite.

Chromite inclusions in uvarovite-chrome garnet, chemically zoned chromite-chrome spinel and chrome spinel-olivine pairs from metacarbonates of the Oetztal-Stubai Complex (northern Tyrol, Austria) are described in terms of their textural occurrences and chemical compositions. Their genetic relationship in relation to the polymetamorphism of the region is discussed.

The ideal formula for members of the cerchiaraite group is Ba4M4(Si4O12)O2(OH)4Cl2[Si2O3(OH)4], where M represents Mn3+, Fe3+ or Al in the octahedral site. A suffix-based naming scheme is used in which the original cerchiaraite is renamed cerchiaraite-(Mn) and two new minerals are named cerchiaraite-(Fe) and cerchiaraite-(Al). The type localities for cerchiaraite-(Fe) are the Cerchiara mine, Liguria, Italy and the Esquire No. 7 and No. 8 claims, Big Creek, Fresno County, California, USA. The type localities for cerchiaraite-(Al) are the Esquire No. 1 claim, Rush Creek, Fresno County, California, USA and the Esquire No. 7 and No. 8 claims noted above. At the Cerchiara mine, cerchiaraite-(Fe) occurs in small fractures and veinlets in a Jurassic ophiolitic sequence. It is of secondary hydrothermal origin and occurs as tan to brown thin prisms and matted fibres. Cerchiaraite(Fe) and cerchiaraite-(Al) from the Esquire No. 1, No. 7 and No. 8 claims occur in parallel-bedded quartz-sanbornite vein assemblages which formed as a result of fluid interaction along the margin of the vein. At the Esquire No. 1, No. 7 and No. 8 claims, both cerchiaraite-(Fe) and cerchiaraite-(Al) occur as subparallel aggregates of blue to bluish green irregular prisms. Both minerals are transparent with a vitreous lustre, Mohs hardness ~4½ , brittle tenacity, irregular fracture and no cleavage. The calculated density of cerchiaraite-(Fe) is 3.710 g cm-3; the measured density of cerchiaraite-(Al) is 3.69(3) g cm-3and the calculated density is 3.643 g cm-3. Cerchiaraite-(Fe) is uniaxial (+), with ω = 1.741(2) and ε = 1.768(2); it is weakly pleochroic and O is colourless and E is yellow. Cerchiaraite-(Al) is uniaxial (-), with ω = 1.695(2) and e = 1.677(2); it is strongly pleochroic and O is colourless and E is blue. Electron-microprobe analyses yielded empirical formulae ranging from (Ba3.82Na0.02Ca0.04)Σ3.88(Fe3+3.42Ti4+0.27Al3+0.25Mn3+0.04Mg0.02)Σ4.00Si5.62O15.47(OH)9.31Cl2.22 (Cerchiara mine) to Ba4.00(Al3+2.40Fe3+1.12Mg0.15Fe2+0.12Mn2+0.06)Σ3.85Si5.78O15.34(OH)8.75Cl2.91 (Esquire No. 1 claim). Cerchiaraite is tetragonal with Z = 2 and crystallizes in space group I4/mmm. The cell parameters for cerchiaraite-(Fe) are a = 14.3554(12), c = 6.0065(5) Å and V = 1237.80(5) Å3; those for cerchiaraite(Al) are a = 14.317(4), c = 6.0037(18) Å and V = 1230.6(6) Å3. In the cerchiaraite-(Fe) structure, SiO4 tetrahedra share corners forming a four-membered Si4O12 ring. The ring is corner-linked to an edgesharing chain of Fe3+ O6 octahedra running parallel to c. A Cl site alternates along c with the Si4 O12 ring. A large channel in the framework contains Ba atoms around its periphery and statistically distributed Si2 O7 silicate dimers and Cl atoms. The strong blue pleochroic colour is attributed to Fe2+ - Fe3+intervalence charge transfer along the octahedral chain.

Minjiangite, ideally BaBe2(PO4)2, is a new mineral species which has been found in the Nanping No. 31 pegmatite, Fujian Province, southeastern China. It occurs in the fractures of montebrasite from pegmatite zone IV, and is associated with quartz, muscovite, hydroxylapatite and palermoite. Minjiangite forms subhedral to euhedral white crystals from 5 to 200 μm long, transparent to translucent, with a vitreous lustre. The estimated Mohs hardness is ∼6, the tenacity is brittle and no cleavage was observed. The calculated density is 3.49 g/cm3. Optically, minjiangite is uniaxial (+), with ω = 1.587(3), ε = 1.602(2) (λ = 589 nm). Electron-microprobe analyses (average of 8) give P2O5 40.16, BaO 43.01, BeO 14.06 (measured by Secondary Ion Mass Spectrometry), SiO2 0.17, CaO 0.17, SrO 0.08, FeO 0.03, MgO 0.01, TiO2 0.07, K2O 0.05, Na2O 0.11, total 97.92 wt.%. The empirical formula, calculated on the basis of 8 O a.p.f.u., is (Ba0.99Ca0.01Na0.01)Σ1.01Be1.98(P1.99Si0.01)Σ2.00O8. The powder X-ray diffraction (XRD) pattern of minjiangite perfectly fits that of synthetic BaBe2(PO4)2; the strongest eight lines of the powder XRD pattern of the natural phosphate [d in Å (I)(hkl)] are: 3.763(100)(101); 2.836(81.3)(102); 2.515(32.3)(110); 2.178(25.6)(200); 2.1620(19)(103); 2.090(63.9)(201); 1.770(16.2)(113); 1.507(25.4)(212). Unit-cell parameters, refined from the powder XRD pattern of natural minjiangite, are a = 5.030(8), c = 7.467 (2) Å, V = 163.96(3) Å3. These unit-cell parameters confirm that minjiangite is the natural analogue of synthetic BaBe2(PO4)2(P6/mmm, a = 5.029(1), c = 7.466 (1) Å, V = 163.52(1) Å3, Z = 1); its crystal structure is topologically similar to that of dmisteinbergite, CaAl2Si2O8, a hexagonal polymorph of anorthite. The formation of minjiangite is related to the hydrothermal alteration of montebrasite by late Ba- and Be-rich fluids.

The influence of both sulphate ions and aspartic acid on directing the growth of baryte has been explored using computer simulation. Both species are found to significantly reduce the activation free-energy to growth under appropriate conditions, with the influence of sulphate being surface specific. This offers the potential for a new approach to morphology control without inhibition that may have implications for biomineralization.

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.

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, singlecrystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. Thechemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)Σ=6.06(Mg0.01Ca1.93Ba0.40)Σ=2.34(Fe0.023+Al10.55Si21.38)Σ=31.9O64·19.6H2O,compatible with the ideal chemical formula K6Ca2[Al10Si22O64]·20H2O.

Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5),b = 14.111(5), c = 9.943(3) Å at 100 K). Refinement converged with four cationic sites and six H2O sites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/Al-distribution. The Raman spectrum of merlinoite (collected between 100and 4000 cm–1) is dominated by a doublet of bands between 496–422 cm–1, assigned to tetrahedral T–O–T symmetric bending modes. T–O–T antisymmetric stretching is also observed; stretching and bending modes of the H2Omolecules are only clearly visible when using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm–1, assigned to the first overtone of the O–H stretching mode, and a band at 5209 cm–1, due to the combination of H2Ostretching and bending modes. Avery broad and convoluted absorption, extending from 3700 to 3000 cm–1 occurs in the H2O stretching region, while the ν2 bending mode of H2O is found at 1649 cm–1. The powder mid-infraredspectrum of merlinoite between 400–1300 cm–1 is dominated by tetrahedral T–O–T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites,which are often confused due to their close similarity.

If the true values of a number (n) of variables are exactly related by one or more (m) equations but all experimental values are liable to experimental error then, provided the errors of measurement can be assumed to be symmetrically distributed about a zero mean, provided the relations are linear, and provided the assessed probable errors of measurement of the several variables remain in constant ratio from one set of measurements to another, the best estimate of the relations derived from N sets of measurements will be given by the latent vectors corresponding to the m smallest latent roots of the n-square matrix whose terms are Σwi ξij ξik (summed from (summed from i = 1 to i = N) for all j and k from 1 to n, where wi is the weight of the ith set of measurements and ξij is the standardized value of the ith measurement of the jth variable measured from its weighted mean.

It is also shown that the alleged inconsistency of the maximum-likelihood estimate of the variance in such a case is simply a confusion of the root-mean-square residual with the root-mean-square normal residual.

An Autocode computer programme has been written to carry out the necessary operations for correlating the physical properties and chemical properties of an isomorphous series of minerals using this procedure.