The chemical analyses, structural formulae, and optical data of seven orthopyroxenes and six clinopyroxenes, all from the charnockite series of Amaravathi, are presented. The orthopyroxenes are in the hypersthene-ferrohypersthene range while the clinopyroxenes are in the sahlite range. The aluminous nature of the pyroxene is believed to be the result of high pressure. The clinopyroxenes have the granulite trend on the Wo-En-Fs plot. The tie-line projections and the KD values for the pyroxene pairs indicate conditions of chemical equilibrium around 670 °C for the charnockite series of Amaravathi.

Two different parageneses for cebollite, a rare hydrated calcium aluminium silicate, are described, both differing from all previously reported occurrences.

Cebollite forms concomitantly with natrolite from plagioclase in xenoliths of crustal material incorporated in kimberlite. The mineral also occurs as a late stage primary mineral in a phlogopite-rich kimberlite.

Tentative models for the genesis of the mineral in the environments described are proposed. It is suggested that the final stages in the crystallization of diatreme-facies kimberlite are dominated by fluids rich in lime and having a low partial pressure of CO2.

The mineralogy and major-element geochemistry of thirty-seven samples from a borehole in the Upper Cretaceous Chalk (Santonian) of Kent has been determined. The mean carbonate content is 97% and the carbonate is a low-Mg calcite (0.42 mol % MgCO3). Most of the silica is deduced to be biogenic chert. The total clay content probably varies through the sequence due to changes in the rate of carbonate sedimentation. The clay composition remains relatively constant with smectite more abundant than illite. The smectite and K-feldspar could be formed from volcanic debris whereas illite and quartz are thought to be detrital.

Over the last 50 years many definitions of element substitution series have been proposed for describing natural Fe-Li micas with complex chemical compositions. In order to compare these definitions and ascertain their reliability, a new geometric frame composed of ideal mica points, mica joins (segments), substitution vectors and substitution planes is constructed to express the entire substitution system of ideal Fe-Al-Li micas. The frame is built in composition space with the coordinate system (0; Si, AlVI AlIV, Fe2+, Li, □VI, K), but has a 3-dimensional analogue, i.e. a visual image.

Using this frame, it has been proved that there are only five possible types of replacement for definitions of Fe-Li micas, and that all possible types have been suggested except the AlIV-constant. Furthermore, it has been proved that the main point in different definitions is that the replacement of Li by Fe2+ needs to be balanced with AlIV, AlVI, or □VI. In order to solve this problem, a set of formulae determining spatial relations between geometric elements in the frame is suggested. With these formulae, the abstract frame is suggested to be a datum system used to ascertain quantitatively the reliability of definition of natural Fe-Li micas.

We revise the data fitting in our original paper [The dissolution rates of simulated UK Magnox - ThORP blend nuclear waste glass as a function of pH, temperature and waste loading, Miner. Mag.79 (2015) 1529–1542]. The intrinsic rate constant data were calculated incorrectly, the corrected data are presented herein. To support the corrected analysis we have also taken the opportunity to report some additional 90°C data. The conclusions of the original paper remain sound.

Bohdanowiczite was first described in 1967 but incomplete data prevented its acceptance as a new mineral at that time. Additional data on the same material now characterize bohdanowiczite as a new species with the formula:

3[(Ag0.98Cu0.02)0.97(Bi0.97Pb0.03)1.02(Se0.83S0.17)2.01]

The mineral occurs in intimate intergrowths with clausthalite and wittichenite in polymetallic mineralization at Kletno in Poland. In reflected light bohdanowiczite has a creamy-yellow colour and short polysynthetic twinning is frequently observed. Cell parameters indexed on a hexagonal lattice are a = 4.183±0.008 Å and c = 19.561± 0.016 Å. Pm1 is the most likely space group. The strongest lines of the powder pattern are 2.91(100), 2.03(30), 3.40(20), 6.54(20), 2.09(18), 3.26(18). The calculated density is 7.72 gm/cm3 and the VHN between 63 and 96 kg/mm2.

Guite (IMA2017-080), Co3O4, is a new mineral species and an important economic mineral found in the Sicomines copper-cobalt mine, located ~11 km southwest of Kolwezi City, Democratic Republic of Congo. The mineral occurs as a granular agglomerate, 50 to 500 μm in size, and is associated closely with heterogenite in a quartz matrix. Guite is opaque, has a dark grey colour with metallic lustre and a black streak. In reflected light microscopy, it is white with no internal reflections. The reflectance values (in air, R in %) are: 27.0 (470 nm); 25.6 (546 nm); 25.2 (589 nm), and 24.6 (650 nm). The average of 20 electron-microprobe analyses is Co 71.53, Cu 0.58, Mn 0.67, Si 0.25, O 26.78, total 99.82 wt.%, corresponding to the empirical formula calculated on the basis of 4 O apfu: (Co2+0.92Cu2+0.02Si4+0.02)Σ0.96(Co3+1.98Mn3+0.03)Σ2.01O4.00, with Co2+ and Co3+ partitioned using charge balance. The ideal formula is Co2+Co3+2O4. Guite is cubic with space group Fd$\bar{3}$m. The unit cell parameters refined from the single crystal X-ray diffraction data are: a = 8.0898(1) Å, V = 529.436(11) Å3 and Z = 8. The calculated density of guite is 6.003 g/cm3. The eight strongest observed powder X-ray diffraction lines [d in Å (I/I0) (hkl)] are: 4.6714 (16.7) (111), 2.8620 (18.4) (220), 2.4399 (100) (311), 2.3348 (10.4) (222), 2.0230 (24.8) (400), 1.5556 (26.3) (511, 333), 1.4296 (37.7) (440) and 1.0524 (10.1) (731, 553). The crystal structure of guite was determined by single-crystal X-ray diffraction and refined to R = 0.0132 for 3748 (69 unique) reflections. Guite has a typical spinel-type structure with Co2+ in tetrahedral coordination with a Co2+–O bonding length of 1.941(1) Å, and Co3+ in octahedral coordination with a Co3+–O bonding length of 1.919(1) Å. The structure is composed of cross-linked framework of chains of Co3+–O6 octahedra sharing the equilateral triangle edges (2.550 Å) in three directions [0 1 1], [1 1 0], [1 0 1] with Co2+ filling the tetrahedral interstices among the chains. Guite is named in honour of Prof. Xiangping Gu (1964–).

While examining the fine series of corundums brought from Burma by Mr. C. Barrington Brown, F.G.S., and comparing them with specimens obtained from Ceylon, Southern India, the United States. and other localities, I have been led to devote especial attention to the curious " parting-planes " which are sometimes found in crystals of this mineral, but which, in other cases, appear to be entirely wanting. In making these comparisons, I have had the great advantage of being able to refer to the fine collection of corundums in the British Museum (Natural History) at South Kensington, and have to gratefully acknowledge the advice and assistance which have been so freely afforded to me at all times by Mr. Fletcher and Mr. Miers.

Pentaerythritol tetranitrate, C(CH2ONO2)4, is an interesting compound structurally, since there is, in the molecule, a carbon atom with foul' like groups (–CH2ONO2) attached to it. The molecule is therefore of the type CX4. It was hoped that an examination of the crystals by means of X-rays would show how far the molecule retains its form and symmetry in the crystalline state ; also that some light would be thrown on the configuration of the nitro- (–NO2) group, especially the equivalence or otherwise of the two oxygen atoms of the group—a question which it has not yet been found possible to settle by chemical methods.

New generalized extinction curves, derived from wave-normals located on a circular cone, are presented. They may be used with the universal stage for the accurate location of up to all three of the indicatrix axes, α, β, γ, of any biaxial crystal, or the optic axis of any uniaxial crystal.

The instrument to be described in the following pages is a goniometer of the suspended type. It is intended primarily for tlle examination of small crystals, and by its aid all the usual crystallographic and optical determinations can be readily carried out. In its design the attempt has been made to combine efficiency with simplicity and strength of construction, together with adaptability to very various purposes. The instrument was completed in the spring of 1899, and has been in continuous use in the Mineralogical Laboratory at Cambridge ever since. Other instruments of the same general type were in existence at the time, or have been described during the past twelve years, and several features which were novelties when it was first constructed can no longer lay claim to originality.

In the classification proposed by the author in a previous paper meteorites are divided into five groups according to the ratio of iron to nickel in the nickeliferous iron they contain. In the case of the meteoric irons such a classification, as shown by Farrington's list of analyses, is a natural one, since the structure of the irons, as revealed by etching, varies with the amount of nickel they contain. Thus Group 1, in which the metal is poor ill nickel, with a ratio of Fe to Ni of 13 upwards, includes nickel-poor ataxites, hexahedrites, and Coarsest and coarse octahedrites ; Group 2, in which Fe : Ni =8-13, the rest of the octahedrites from medium to finest ; Group 8, in which Fe : Ni = 5-8, nickel-rich ataxites; Group 4, in which Fe: Ni = 2-5, ataxites still richer in nickel; while Group 5 may include the doubtful Oktibbeha meteorite in which the ratio of iron to nickel is even less than one.

Johninnesite, ideally Na2Mg4Mn12As5+2 Si12043(OH)6,, is triclinic, P1 or P1̄, with a = 10.44(2), b = 11.064(6), c = 9.62(1) Å, α = 107.43(7), β = 82.7(1), γ = 111.6(1)°, V = 894(2) Å3, and Z = 1. It occurs as yellow-brown fibrous aggregates, associated with rhodonite, kentrolite, and richterite, from the Kombat Mine in Namibia. Johninnesite has cleavages on {100} and {010}, density of 3.48 (meas.), 3.51 (calc.) g/cm3. It is biaxial negative, with 2Vx = 41.9°, α = 1.6742(4), β = 1.6968(3), γ = 1.6999(3); dispersion r > υ, distinct.

A preliminary notice of this new mineral, named in honour of Dr. Arthur Hutchinson, Demonstrator of Mineralogy in the University of Cambridge, was read before the Cambridge Philosophical Society in October, 1903. The material was first found, in the white crystalline dolomite of the Lengenbach quarry, during my visit to the Binnenthal in the summer of 1903. More material was received in November of the same year, and a further supply was obtained in 1904.

In 1934 a contribution from America (Parmelee and Badger, p. 2) reported that a certain glaze, containing rutile, showed rapid reversible darkening in daylight. It was stated that C. H. Zwermann, Jr., ascribed this photosensitivity to titanium. In the present author's experience the phenomenon is often exhibited, in varying degrees, by commercial glazes based on rutile or on the purified titanium dioxide available in industry, as well as by glazes made up in the laboratory from chemical titanium dioxide of high purity. Lee, also in America, observed reversible darkening in sunlight in commercial titanium dioxide itself, and the existence of this effect was confirmed by Williamson (1937) for some brands of commercial titanium dioxide available in Britain. These brands were affected by daylight which had passed through glass, and some tentative suggestions were made regarding the mechanism of the reversible darkening. Later it was demonstrated (Williamson, 1939) that reversible darkening in daylight could be produced in a sample of titanium dioxide of considerable purity, which was itself not discoloured by light, by contamination with iron according to a special method.

Well-Crystallized icositetrahedral garnets from Botallack, Cornwall, are preserved in most British mineral collections, but they have previously not been systematically examined. The original specimens were discovered in 1821 by a St. Just miner who dealt in minerals, and the occurrence is first referred to by Carne in his paper 'On the mineral productions and the geology of the parish of St. Just' as follows : 'About six months ago, a mass of beautiful garnets, of a deep red colour, was found imbedded in the rock, not far from low water mark at the foot of Chycornish Carn, about a quarter of a mile south of Botallack. Some of the crystals were larger than hazel-nuts, and most of them were twenty-four sided. Some specimens of a very superior order were procured, each having from one to two hundred crystals on its face.'

Magnesio-arfvedsonite, the CFe3+-dominant analogue of eckermannite, has been found in a sample of “szechenyite” in the mineral collection of the American Museum of Natural History (AMNH H35024). It comes from the northern part of the Jade Mine Tract near Hpakan, Kachin State, Myanmar. Associated minerals are kosmochlor–jadeite solid-solution pyroxene and clinochlore. The ideal formula of magnesio-arfvedsonite is ANaBNa2C(Mg4Fe3+)TSi8O22W(OH)2, and the empirical formula derived from electron microprobe analysis and single-crystal structure refinement for the sample of this work is A(Na0.96K0.04)Σ=1.00B(Na1.57Ca0.40Fe0.022+Mn0.01)Σ=2.00C(Mg4.26Fe0.192+Fe0.413+Al0.11Ti0.034+)Σ=5.00T(Si7.99Al0.01)Σ=8.00O22W[F0.02(OH)1.98]Σ=2.00. The unit-cell dimensions are a = 9.867(1), b = 17.928(2), c = 5.284(1) Å, β = 103.80(2)°, V = 907.7 (2) Å3, Z = 2. Magnesio-arfvedsonite is biaxial (–), with α = 1.624, β = 1.636, γ = 1.637, all ± 0.002 and 2Vobs = 36(1)°, 2Vcalc = 32°. The ten strongest reflections in the X-ray powder pattern [d values (in Å), I, (hkl)] are: 2.708, 100, (151); 3.399, 68, (131); 3.144, 63, (310); 2.526, 60, (202); 8.451, 46, (110); 3.273, 39, (240); 2.167, 37, (261); 2.582, 34, (061); 2.970, 34, (221); 2.326, 33, [(251) (421)].