Blue pleochroic crystals obtained from basic slag were first described by Carnot and Richard. They published a chemical analysis, some of the optical properties, and a brief description of the forms they observed. The crystals were stated to be orthorhombic, with a composition of 5CaO.P205.SiO2. Several authors later described similar crystals. None, however, gave a thorough account of the optical properties. These various papers were summarized and discussed by Kroll, who accepted Carnot's formula, but concluded, from Bücking and Linck's examination, that the material was monoclinic. Kroll applied the rather unfortunate term ‘silico-carnotite’ to these crystals.

The present work shows that silicocarnotite occurs in only one modification–orthorhombic. The crystals drawn by Bricking and Linck and described as monoclinic are, in fact, identical with our orthorhombie crystals.

Blanfordite (a manganiferous aegirine), rhodonite, alurgite, manganophyllite, and piemontite are deseribed from a pegmatite that cuts a manganese ore band in the Sitasaongi mine, Chikla, Bhandara district, India. In addition, rhodonite and piemontite are described from gneiss and schist areas. Chemical analyses and optical properties of all these minerals are given and their possible origin suggested.

The accompanying map is the outcome of a survey of Shetland, conducted during part of several summers.

Almost the whole of the junctions laid down were visited by myself ; for the few that were not, and also for certain of the lines continued inland—which from an almost unbroken covering of peat and turf, are more or less conjectural—I am indebted to Dr. Hibbert's narrative.

To Professor Geikie's map of Scotland I am indebted for the southern limit of the isolated mass of sandstone of the Lerwick district.

Two monoclinic minerals formerly classified as ganophyllite have been differentiated on the basis of single-crystal X-ray data. True ganophyllite occurs at the Harstig mine, Pajsberg, Sweden (a, 16·60 ± 0·05 Å; b, 27·04 ± 0·08 Å; c, 50·34 ± 0·15 Å; β, 94° 10′ ± 10′; space group A 2/a), at the Benallt mine, Caernarvonshire, Wales, and in Aroostook County, Maine. Bannisterite, a new mineral, occurs at Franklin, New Jersey (a, 22·20 ± 0·07 Å; b, 16·32 ± 0·05 Å; c, 24·70 ± 0·08 Å; β, 94° 20′ ± 10′; space group A2/a) and at the Benallt mine, Wales. Both minerals have similar pseudocells: a, 5·53 Å; b, 3·3 Å; c, 25 Å; β, 94° The chemical analysis of ganophyllite from the Harstig mine, Sweden, is: SiO2, 39·67 %; Al2O3, 7·95; Fe2O3, 0·90; MnO, 35·15; CaO, 1·11; MgO, 0·20; PbO, 0·20; K2O, 2·70; Na2O, 2·18; Li2O, trace; H2O, 9·79; total, 99·85. The chemical analysis of bannisterite from Franklin Furnace, New Jersey, is: SiO2 46·20 %; Al2O3, 4·74; MnO, 23·02; FeO, 6·40; ZnO, 4·67; CaO, 1·52; MgO, 1·99; Na2O, 0·29; K2O, 1·21; H2O, 9·74; total, 99·78.

Both ganophyllite and bannisterite show a structural resemblance to stilpnome-lane from Deer Isle, Maine, in projection on selected zones. All three have a micaceous cleavage parallel to {001} in the orientations here taken. Stilpnomelane is triclinic, pseudotrigonal, and pseudomonoclinic. In the triclinic cell, a = b, 22·05 Å ± 0·06 Å; c, 17·70 ±0·06; α, 124° 49′; β, 95° 58′; γ, 120° 00′ (angles ± 5′). In the trigonal subcell, a′, 3·2 Å; c′, 36·4. Small distorted trigonal subcells for ganophyllite have a′, 3·38 Å; c′ 37·7, and for bannisterite have a′, 3·264 and c′, 37 Å.

The very abundant literature dealing with the twinning of felspar phenocrysts has put on record a surprisingly large number of twin-laws. Some of these have such complex indices that they have never been accepted; others are regarded as doubtful. Yet the authors of these have well-established reputations and the accuracy of their observations cannot be doubted. The difficulty lies in the interpretation of the results. Beside numerous examples of well-defined laws, one comes across a high percentage of isolated cases, each appearing quite as plausible as these, yet difficult to assign to any definite law.

Eudialyte-related compounds have been synthesised hydrothermally at T = 600°C and P = 2 kbar from a stoichiometric mixture of Na2CO3, CaO, Fe2O3, ZrOCl2 and SiO2 using the Na:Ca:Fe:Zr:Si ratios corresponding to the eudialyte end-member Na15Ca6Fe3Zr3Si(Si25O73)(OH)Cl2⋅H2O, in the presence of 1 M aqueous solutions of NaCl and NaF. The synthesis was carried out in platinum ampoules over 10 days. Natural raslakite (a Ca-deficient member of the eudialyte group) was used as a seed and added in amounts corresponding to 2 wt.% of the whole charge. The products were characterised by powder X-ray diffraction, IR and Raman spectroscopy, morphological features, and electron probe microanalyses. In experiments with NaCl, almost pure eudialyte-type compounds were obtained. Synthesis in the presence of a NaF solution resulted in the formation of a F-dominant eudialyte-type compound related to raslakite as the main product and aegirine, vlasovite and lalondeite as by-products. All synthesised eudialyte-type compounds are Zr-rich and Fe-deficient, similar to eudialyte-group minerals from hyperagpaitic rocks related to foyaites. The increased NaCl contents in the reaction system results in increased Ca content in the synthesised eudialyte-related compounds. The crystal-chemical formulae of the synthesised eudialyte-type compounds are derived based on general regularities established earlier for eudialyte-group minerals.

The new triazolate mineral bojarite (IMA2020-037), Cu3(N3C2H2)3(OH)Cl2⋅6H2O, is found in a guano deposit located at the Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile. Associated minerals are salammoniac, halite, nitratine and belloite. Bojarite occurs as blue fine-grained porous aggregates up to 1 mm × 3 mm × 5 mm combined typically in interrupted earthy crusts. The mineral is brittle. The Mohs hardness is 2. Dcalc = 2.057 g cm–3. The IR and Raman spectra show the presence of the 1,2,4-triazolate anion and H2O molecules. Bojarite is optically isotropic and n = 1.635(2) (λ = 589 nm). The chemical composition (electron-microprobe data for Na, Mg, Fe, Cu and Cl; H, C and N contents measured by gas chromatography on products of ignition at 1200°C; wt.%) is: Na 0.22, Mg 0.74, Fe 0.99, Cu 29.73, Cl 13.62, N 20.4, C 11.6, H 3.3, O (calculated by stoichiometry) 19.93, total 100.53.

The empirical formula is (Cu2.68Mg0.17Fe0.10Na0.05)Σ3(N3C2H2)2.755[(OH)][Cl2.19(H2O)3.77(OH)0.04]Σ6⋅2.3H2O. The idealised formula is Cu3(N3C2H2)3(OH)Cl2⋅6H2O. The crystal structure of bojarite was refined based on powder X-ray diffraction data, using the Rietveld method. The final agreement factors are: Rp = 0.0225, Rwp = 0.0310 and Robs = 0.0417. The new mineral is cubic, space group Fd$\bar{3}$c; a = 24.8047(5) Å, V = 15,261.6(5) Å3 and Z = 32. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%)(hkl)] are: 8.83 (31)(220), 7.19 (100)(222), 6.23 (35)(400), 5.077 (28)(422), 4.194 (28)(531), 3.584 (23)(444), 2.865 (28)(660, 751) and 2.723 (22)(753, 842).

Syntheses in acidified hydrothermal (HT) solutions (1 N H2SO4 or stronger) produce monoclinic non-stoichiometric K-jarosites which contain Fe-site vacancies with long-range order. Syntheses in non-acidified HT solutions produce rhombohedral K-jarosites which contain relatively large numbers of Fe-site vacancies with no long-range order. Increasing the [Fe]/[K] ratio, reaction temperature and reaction time in non-acidified solutions promotes the formation of monoclinic jarosites which contain Fe-site vacancies with short-range order. A structural model including details of the ordering of the Fe-site vacancies was obtained by refinement of single-crystal synchrotron data from one of the HT synthesis products; this model was used to refine synchrotron powder X-ray diffraction data from products synthesized at different reaction times, temperatures and [Fe]/[K] ratios. Thermal and chemical analyses are consistent with a model for non-stoichiometry in which domains of stoichiometric jarosite are intergrown with butlerite-like iron-deficient domains with a composition [Fe2(SO4)2(OH)2(H2O)4]. It was found that heterogeneous nucleation of monoclinic jarosite on Si disks is preceded by the formation of an oriented film of Maus's Salt, K5Fe3O(SO4)6·10H2O, as a precursor phase, and that this transforms topotactically into oriented jarosite, which contains butlerite-like layers parallel to the disk surface. Structural models for the transformation of Maus's Salt into jarosite are proposed.

Found by N. Theis at a uranium prospect near Durango, Colorado. Occurs with uraninite, galena, malachite, azurite, etc. Colour pale blue-green, H = 1½, G = 4.25. Optically 2Vα ≈ 0°, α = 1.755, β = γ = 1.785; non-pleochroic. Chemical analysis on 1034 µg gave CuO 33.3 %, ZnO 33.1, CaO 0.3, As2O5 14.8, Sb2O5 7.0, H2O 10.5 leading to Cu5Zn5{(As,Sb)O4}2(OH)14. The cell indexes as orthorhombic a = 8.225Å, b = 7.123, c = 14.97. Strongest lines are 14.97 (9), 7.483 (5), 4.112 (4), 3.741 (10), 2.996 (4), 2.534 (9), 1.830 (5), 1.553 (3). The mineral and name have been approved by the Commission on New Minerals and Mineral Names, IMA.

Cesium kupletskite has been renamed kupletskite-(Cs) with the approval of the IMA Commission on New Minerals, Nomenclature and Classification, because the name of a mineral species should be a single word and the International Union of Pure and Applied Chemistry spelling is caesium. The presence or absence of parentheses around the suffix chemical-element is discussed. The advantages of the chemical-element suffix nomenclature are stated.

Copper-sulfides within carbonatites and phoscorites of the Phalaborwa Igneous Complex, South Africa, have been investigated since the middle of the 20th Century. However, aspects of ore formation have remained unclear. This study examines the mechanisms involved in Cu-sulfide mineralisation by micro-focus X-ray computed tomography as applied to sulfide-rich drill core samples. Several texturally distinct assemblages of magmatic sulfides can be identified, including: (1) <500 μm rounded bornite and chalcopyrite grains disseminated within the gangue; (2) elongated mm-scale assemblages of chalcopyrite and bornite; and (3) mm-to-cm thick chalcopyrite cumulates. Chalcopyrite veins were also observed, as well as late-stage valleriite, documenting late-stage fluid circulation within the pipe, and alteration of magmatic and hydrothermal sulfides along fractures within the gangue, respectively. The results of micro-focus X-ray computed tomography indicate that magmatic sulfides are sub-vertically aligned. Spatial variability of the sulfide assemblages suggests that textural changes within sulfide layers reflect fluctuating magma flow rate during emplacement of carbonatite–phoscorite magmas, through coalescence or breakup of sulfide liquid droplets during ascent. Modal sulfide abundances, especially for disseminated assemblages, differ from one carbonatite–phoscorite layer to another, suggesting a strong control of the mechanical sorting in the formation of Cu-sulfide textures within the Loolekop carbonatite. The alternation of carbonatite and phoscorite within the intrusion suggest that the Loolekop Pipe was emplaced through a series of successive magma pulses, which differentiated into carbonatite and phoscorite by melt immiscibility/progressive fractional crystallisation and pressure drop. Three-dimensional textural analysis represents an effective tool for the characterisation of magma flow and is useful for the understanding of magmatic processes controlling sulfide liquid-bearing phoscorite–carbonatite magmas.

Bosoite (IMA2014-023) is a new silica clathrate mineral containing hydrocarbon molecules in its crystal structure. Bosoite can be considered structurally as a silica analogue of the structure-H gas hydrate, where guest molecules are trapped in cage-like voids constructed of the host framework. The mineral occurs in the Miocene tuffaceous sedimentary rocks at Arakawa, Minami-boso City, Chiba Prefecture, Japan. Bosoite is hexagonal, and it crystallises as an epitaxial intergrowth on chibaite crystals, with the {0001} of bosoite parallel to octahedral {111} form of chibaite. Crystals are colourless and transparent with vitreous lustre. The calculated density is 2.04 g/cm3. The empirical formula (based on 2 O apfu and guest molecules assumed as CH4) is Na0.01(Si0.98Al0.02)Σ1.00O2⋅0.50CH4; the end-member formula is SiO2⋅nCxH2x+2. Bosoite has the space group P6/mmm, with the unit-cell parameters a = 13.9020(3) Å, c = 11.2802(2) Å, V = 1887.99(6) Å3 and Z = 34. The crystal structure of bosoite was refined by single-crystal X-ray diffraction and converged to R1 = 4.26% for the average model and R1 = 2.96% for the model where all oxygen sites are split.

Although the Mendip Hills, as a district, have from time to time received the attention of geologists, details of the mineral occurrences are, on the whole, remarkably scarce. Mining was formerly carried on on the Hills for many centuries, but mineralogy as a science had not been sufficiently developed at the time when the mines were most active, and little interest was taken in the minerals other than those suitable or required for commercial and industrial purposes. Even in later years, when, in the course of treating old refuse and tailings left by earlier miners and of various attempts to resuscitate the mining industry, much material must have been available for examination, little attention seems to have been paid to it, or to the numerous quarries that were opened in the Carboniferous Limestone.

If the planes of a crystal be replaced by lines drawn perpendicular to them through a point the intersection of the sheaf of lines so formed with the plane of the paper is the Gnomonic Projection of the crystal; each face being represented by a point and each zone by a line joining two such points. This projection, which has been frequently used and fully described, has generally been employed to represent the symmetrical disposition of the faces, the plane of the figure being a plane of symmetry.

But the practical value of the projection is best seen when it is used either as a graphic representation of the forms of a mineral, or as a method of drawing a perspective figure of any part of a crystal.

Electron micrographs of Na-saturated Unter-Rupsroth montmorillonite show that many of the individual flakes, which are probably 10 Å. thick, have straight edges meeting in 120° angles. This is evidence in support of the pseudohexagonal structure of montmorillonite. Similar pictures were obtained with Lisaturated clay and with ‘Calgon’-dispersed material. The usefulness of electron microscopy for the study of clay mineral morphology depends upon the efficiency of dispersion and the details of the mounting techniques rather than the nature of the exchange cation or the particular dispersing agent employed.