Nickolayite, FeMoP, is a new terrestrial phosphide structurally related to allabogdanite (high-pressure modification of (Fe,Ni)2P), and the meteoritic phosphides florenskyite, FeTiP and andreyivanovite, FeCrP. From the point of view of chemical composition, nickolayite is an Fe-analogue of monipite, MoNiP. The mineral was discovered in the Daba-Siwaqa complex, Central Jordan, a part of the pyrometamorphic Hatrurim Formation (the Mottled Zone), whose outcrops encompass a 150 × 200 km area around the Dead Sea in the Middle East. Nickolayite appears as an accessory phase in the fused clinopyroxene–plagioclase rocks texturally resembling gabbro–dolerite. The irregularly shaped grains of the mineral, up to 80 μm in size are associated with baryte, tridymite, chromite, hematite, pyrrhotite, fluorapatite, titanite and powellite. Macroscopically, nickolayite grains possess light-grey to greyish-white colour and metallic lustre. The mineral is ductile. The mean VHN hardness (50 g load) is 538 kg mm–2. The calculated density based on the empirical formula and the unit-cell parameters is 7.819 g cm–1. In reflected light, nickolayite has a white colour, with no bireflectance or pleochroism. The COM approved reflectance values [Rmax/Rmin (%), λ(nm)] are: 48.5/46.5 (470), 50.5/48.5 (546), 51.8/49.9 (589) and 53.9/52.0 (650). The chemical composition of the holotype crystal is (electron microprobe, average of 4 analyses, wt.%): Fe 32.21, Mo 47.06, Ni 3.69, Co 0.13, P 17.45, total 100.54, that corresponds to the empirical formula Fe1.00(Mo0.87Ni0.11Fe0.02)Σ1.00P1.00 and an ideal formula of FeMoP. Nickolayite is orthorhombic, space group Pnma, unit-cell parameters of holotype material are: a = 5.9519(5), b = 3.7070(3), c = 6.8465(6) Å, V = 151.06(2) Å3 and Z = 4. The crystal structure of holotype material was solved and refined to R1 = 0.0174 based on 251 unique observed reflections. The origin of the mineral is probably connected to the processes of co-reduction of molybdenum- and phosphorus-bearing minerals during high-temperature pyrometamorphic processes.

The rapid determination of the chemical elements present in a mineral has been a desideratum ever since minerals became of economic use. Various methods have been employed, starting with blowpipe work, which in the early days proved of great value, especially in experienced hands, With the development of chemistry and the discovery of new elements, this process was largely abandoned in favour of the standard ' wet method' of chemical analysis. Later on, micro-chemical reactions came into limited employment. Here the appearance of easily crystallizable salts under the microscope was used for diagnostic purposes. This method has been extensively examined of late years and became so overloaded with precautions that its chief asset, that of rapidity and case of employment, has been largely lost. Quite recently colorimetric reactions have been applied to qualitative analysis. These appeared so promising that the present author was encouraged to endeavour to apply them to the examination of minerals.

A scheme for the qualitative determination of the commoner elements was published by G. Gutzeit in 1929, which at first sight looked very attractive.

Bavenite was first described from Baveno by Artini in 1901 as monoclinic crystals of prismatic habit in pegmatitic druses in granite and given the formula 3CaO.Al2O3.6SiO2.H2O. More recently, the mineral has been described pseudomorphous after beryl from Himalaya mine, Mesa Grande, San Diego County, California, by Schaller and Fairchild (1932) and shown to contain beryllium as an essential constituent. In 1933 X-ray determinations by Ksanda and Merwin indicated a unit cell with dimensions a 9·67, b 11·53, c 4·95Å, and showed the symmetry to be orthorhombic and referable to the space-group V1, Vh1, or C2v1. Revised crystallographic orientation and optical constants were also suggested by these authors.

The material about to be described is from two localities in Switzerland. Of fourteen specimens from a fissure in the rocks below the Muotta Nera, Piz del Laiblau, Val Nalps, Tavetschthal, Graubünden, selected by Mr. F. N. Ashcroft in 1935 and 1936 from a fairly large series stocked by Adolf Caveng of Sedrun, one (B.M. 1937,598) carries the mineral as roughly radiating aggregates of platy fibres of very pale brown colour in bulk.

The mineral to be described was found by Mr. C. T. Clough, M.A., of the Geological Survey, near the junction of the two large streams in Coire Dhorrcail, near Barrisdale on the south side of Loch Hourn, Inverness-shire.

Mr. Clough furnishes me with the following description of the mode of occurrence of the mineral :—

‘The crystals were obtained from a band, which, although its sides are not well exposed, seems to form a nearly horizontal vein-like mass. This band crosses both the bedding and the foliation planes of the muscovite-biotite-gneiss in which it occurs, and which occupies a large area near Barrisdale and Ladhar Bheinn.

The geometrical representation of the faces and edges of a crystal is obtained (i) by drawing lines through a fixed point O perpendicular to each crystal-face meeting a fixed sphere with centre O in a point (face-pole) representing that face, (ii) by drawing lines through O parallel to each crystal-edge meeting the sphere in a point (edge-pole) representing that edge. This representation is inconvenient as being in three dimensions, and therefore it is customary to map the sphere on a plane. This is usually done by means of the stereographic or gnomonic projection.

Minium occurs at Broken Hill, New South Wales, as pseudomorphs after cerussite, formed during fires in the mine. It is tetragonal with a = 8·824 Å. and c = 6·564 Å.; sp. gr. 8·2 + 0·2. The Broken Hill minium appears identical in physical properties with synthetic Pb3O4 described by other workers.

During an examination of the mineral bayldonite, (Pb,Cu)7(AsO4)4(OH)2.H2O, for the purpose of obtaining standard X-ray powder data to compare with supposed single crystals of this species, it was found that a specimen purchased in 1948 as bayldonite from Ojuela mine, Mapimi, Durango, Mexico (B.M. 1948,267) gave a powder pattern related to those of members of the descloizite group and fairly close to but not identical with conichalcite, CuCaAsO4OH. It chanced that about the same time a specimen of a green botryoidal mineral from Brandy Gill, Caldbeek Fells, Cumberland, sent in by Mr. W. F. Davidson for determination was photographed and showed similar variations from the conichalcite pattern. Qualitative spectrographic comparison of the Mapimi and Brandy Gill materials with several conichalcites suggested that the differences in the powder photographs might be due to the presence of lead in the former.

The theoretical basis for the stability of binary and quasi-binary solutions is discussed with special emphasis on miscibility relations. Solutions of the distribution equations are presented for the case of two and three coexisting regular solutions and this model is used to illustrate the energetics of miscibility relations. The same principles are then extended to give a qualitative interpretation to sequences of mineral assemblages consisting of pyroxenes, amphiboles, micas, and feldspars. A formulation is presented for the intrinsic stability of a solution, which depends on the presence or absence of an excess free energy of mixing, and the extrinsic stability of a solution, which depends on the standard free energy of the component end members.

A rock from the Mt. Painter area, South Australia, consists essentially of corundophilite (anal., X-ray) and corundum, with accessory boehmite, sapphirine, cordierite, muscovite, and rutile. The rock probably crystallized at 500 to 700°C under 20 000 Ib/in.2 pressure, boehmite being formed by retrogressive metamorphism at 120 to 280° C.

The spherulitic rhyolites of Jersey show a development probably unequalled in the British Isles. They are particularly notable for the large size of the spherulites and for the variety of structures which they present. The object of the present paper is to describe some of these structures and to discuss their origin.

The first worker to publish a description of spherulitic rhyolites from Jersey was Davies (2). Their field relations were described by Noury (4), while De Lapparent has discussed their petrology (5), (8) and the vexed question of their age (7). Parkinson (10), (12), (14) has given admirable and detailed accounts of the Bouley Bay rocks.

Heyite (see preceding paper) is so strikingly similar to brackebuschite that a close comparison of the two species seemed advisable. Topotype brackebuschite (B.M. 55819) was used for this purpose.

Brackebuschite is a vanadate of lead, manganese, and iron, heyite a vanadate of lead and iron. Both species are monoclinic with diffraction symmetry P21 or P21/m. The X-ray cells are remarkably close: a = 8·810, 8·910; b = 6·155, 6·017; c = 7·651, 7·734; β = 111° 30′, 111° 53′ (brackebuschite first). As might be expected, powder patterns are strikingly close as well.

Other than the similarities noted above, the minerals differ so fundamentally that they cannot be the same—they are valid and distinct species. Optic orientations show α: [001] 20° (in acute β) for brackebuschite, 36° (in obtuse β) for heyite. Indices are (brackebuschite first): α 2·28, 2·185; β 2·38, 2·219; γ 2·49, 2·266 for the sodium D line.

Chemical differences are irreconcilable and reaffirm brackebuschite as Pb2(Mn,Fe,Zn)(VO4)2.H2O while heyite is Pb5Fe2(VO4)2O4.

The crystal structure of magbasite from the Eldor carbonatite complex, Quebec, Canada, has been determined and indicates that the currently accepted formula should be revised to KBaFe3+Mg7Si8O22(OH)2F6. Magbasite is orthorhombic, space group Cmme (Cmma), with unit-cell parameters a 18.9506(3) Å, b 22.5045(3) Å, c 5.2780(1) Å, V 2250.93(6) Å3 (Z = 4). The structure has been solved and refined to final agreement indices R1 = 0.026, wR2 = 0.052, GooF = 1.116 for a total of 2379 unique reflections, and is a new kind of trellis motif related to amphibole and carpholite topologies. An amphibole-like I-beam ‖(100) of edge-sharing octahedrally-coordinated M(1,2,3) sites, which are filled by Mg, is sandwiched between double-chains of SiO4 tetrahedra ‖c. This I-beam is connected to side-ribbons ‖(010) of edge-sharing (Mg,Fe2+)O4(OH,F)2 and Fe3+O4(OH)2 octahedra to form a tunnelled box or trellis structure very like that of carpholite, for which the I-beams are pyroxene-like. K occupies a tunnel site analogous to the A site of amphibole. Ba occupies a cavity site at the corners where the I-beam and side-ribbon meet, and corresponds to the A site of carpholite. The structural relations between magbasite and carpholite are discussed.

The hyalotekite group has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (memorandum 57–SM/16). The general formula of the minerals of the hyalotekite group may be written as: A2B2M2[Si8T4O28]W where A = Ba2+, Pb2+ or K+; B = Ba2+, Pb2+ or K+; M = Ca2+, Y3+ or REE3+; T = Si4+, B3+ or Be2+; and W = F– or □ (where REE = rare-earth elements and □ = vacancy).

Four minerals are currently known in this group: hyalotekite, Ba4Ca2[Si8B2(SiB)O28]F, triclinic, I$\bar 1$; khvorovite, Pb2+4Ca2[Si8B2(SiB)O28]F, triclinic I$\bar 1$; kapitsaite-(Y), Ba4(YCa)[Si8B2B2O28]F, triclinic, I$\bar 1$; and itsiite Ba4Ca2[Si8B4O28]□, tetragonal, I$\bar 4$2m.

We explore the possible end-member compositions within this group by conflating the properties of an end-member with the stoichiometry imposed by the bond topology of the hyalotekite structure-type and the crystal-chemical properties of its known constituents. There are two high-coordination sites in the hyalotekite structure, A and B, and occupancy of each of these sites can be determined only by crystal-structure refinement. If these two sites are considered together, there are 19 end-member compositions of the triclinic structure and six end-member compositions of the tetragonal structure involving A and B = Ba2+, Pb2+, K+; M = Ca2+, Y3+, REE3+; and T = Si4+, B3+, Be2+. There is the possibility for many other hyalotekite-group minerals, and two potential new minerals have been identified from data in the literature.

Small crystals (2 mg.) of plagioclase and potassium felspar were irradiated for four weeks in an atomic pile. Subsequent analysis of the radiation showed that this is a possible method for the determination of the sodium and potassium content, and it should be possible to develop the method further in this direction. It has not proved a suitable method for the determination of calcium.

Thirty-Four specimens of australites were collected by Miss N. Jones and her brother Mr. Jones, during forty years while working on their property of 2000 acres, on the north bank of the Glenelg river. This is situated 3½ miles due east of Harrow (37° 8' S., 141° 33' E.) in the western district of Victoria, 236 miles north of west of Melbourne. The collection was kindly submitted for examination through Mr. E. D. Gill of the National Museum, Melbourne.

Polloneite, ideally AgPb46As26Sb23S120, is a new N = 4 member of the sartorite homologous series. It occurs in a matrix of baryte from the Pizzone level of the Pollone baryte-pyrite-(Pb-Zn-Ag) deposit at Valdicastello Carducci, near Pietrasanta, in the Apuan Alps, Tuscany, Italy, as anhedral grains up to 0.5 mm across. The mineral is opaque, greyish black with a metallic lustre. In reflected light polloneite is white, bireflectance is moderate. Internal reflections are absent. Under crossed polars, anisotropism is moderate with rotation tints in brown-violet and deep grey. The reflectance data (%, air) are: 30.2, 42.4 at 470 nm, 28.8, 41.0 at 546 nm, 27.9, 39.8 at 589 nm and 26.0, 37.4 at 650 nm. Mohs hardness is 3–3½, microhardness VHN50 exhibits a mean value of 200 kg mm-2. The average results of 15 electronmicroprobe analyses of three grains are Ag 0.71(5), Pb 52.05(21), As 10.61(22), Sb 15.40(12), S 21.16(8), total 99.92(15) wt.%, corresponding to Ag1.20Pb45.76As25.79Sb23.04S120.21 (on the basis of Me + S = 216 apfu). The simplified formula AgPb46As26Sb23S120 is in accordance with the results of a crystal structure determination. The calculated density is 5.77 g cm–3. Polloneite is monoclinic, space group P21, a = 8.413(2), b = 25.901(5), c = 23.818(5) Å, β = 90.01(3)°, V = 5189.8(18)Å3, Z = 1. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)hkl] are 3.795(100)(026), 3.414(60)(233), 3.238(69)(080), 3.020(97)(253), 2.922(82)(066), 2.738(73)(236), 2.375(79)(290) and 2.103(64)(400). Polloneite is a new N = 4 member of the sartorite homologous series with substantial Sb and small, but important, Ag content. It is a three-fold superstructure with a tripled unit-cell parameter, 7.9 Å, of sartorite homologues. In the As-Sb rich slabs, several types of crankshaft chains and isolated (As,Sb)–S polyhedra occur. A sequence of three different, tightly bonded double-layer fragments (broad ribbons) contains two asymmetric fragments with long crankshaft chains whereas the third fragment type, with Ag, contains small mirror-symmetrical metalloid groups and no crankshaft chains. This configuration can potentially cause order-disorder phenomena in the structure. The threefold superstructure and the mixed As-Sb character distinguish polloneite from veenite and from dufrénoysite, respectively.

A design for a micro furnace and a fusion technique are described by which silicate materials (in particular picritic and peridotitic rock compositions) may be fused and quenched to a homogeneous glass without significant loss of components, for the purposes of bulk analysis. The furnace consists of a Pt wire electrical resistance heater mounted in a furnace assembly which is fitted to a microscope stage. Microscopic examination of the sample during the fusion process allows the sample to be quenched as soon as all crystalline material has been fused and thus minimizes the loss of iron and alkalis due either to over-heating or prolonged fusion time. Analysis of glass beads of a model peridotite composition (analysed independently by X-ray fluorescence analysis) shows that for typical fusion times (5–10 seconds) the bulk composition is preserved at distances of > 25 µm from the margins of the glass beads. Analysis of natural rock powders of known composition shows that the method can be used to analyse whole rock compositions. The furnace is simple to construct and cheap to run and provides a simple and rapid method of producing glass samples for bulk analysis.