The cell parameters of 35 members of the arfvedsonite-eckermannite series and catophorites (17 from the literature, 18 newly determined) are presented and an attempt made to relate them to chemical composition. In general, all parameters (including β, obtuse) decrease from arfvedsonite to eckermannite, but for different reasons: a, b, and β (very slightly) as the Mg: Fe2+ ratio and F increase; c as Fe3+ decreases. The apparent decrease in a and b with high Li is coincidental, due to its strong correlation with F, which varies inversely With (OH). In addition, b is increased by high Ca and slightly reduced by high A1.

Also, the empirical and calculated curves relating MgO and total iron as Fe2O3 (weight %) with the Mg ratio, 100 Mg/(Mg + Fe2+ Fe3+ + Mn), for all amphibole groups are given, as a rapid method of obtaining an estimate of the Mg ratio.

The full lists of possible hkl values for an arfvedsonite and an eckermannite are enumerated up to 45° 2θ, Cu-Kα, to illustrate the difficulty in indexing X-ray photographs and diffractometer charts of this group.

The muscovites are 2M1 polymorph type; minimum temperature of crystallization of 435 °C is obtained from the molecular percentage of paragonite in muscovite.

Cowlesite specimens from nine new occurrences in Northern Ireland and from eight localities previously reported in the literature, were crystal-chemically characterised. The chemical data for a total of 25 samples indicate a composition close to the stoichiometric formula for cowlesite and a very limited compositional range. X-ray powder diffraction spectra were performed on 8 samples. The crystallographic unit cell permit a proper indexing of the X-ray powder diffraction patterns as orthorhombic, unit cell constants close to a 23.3, b 30.6, c 25.0 Å and doubled with respect to those originally reported in literature. The powder pattern and the TG curve arc reported for an unidentified mineral species associated with cowlesite in one of the samples from Northern Ireland.

Harmotome, associated with analcime, is described from andesite dykes at Rehia and Maungarahu in the Tokatoka district, New Zealand. The Maungarahu harmotome has the composition: (Na1·03K0·23)(Ba1·54Ca0·18)Al4·66Si11·31 12·39 H2O; physical properties: α 1·498, β 1·503, γ 1·506, 2Vγ 75–82° β:[001] 28° D 2·378; and cell constants: a 9· 906±0·006, b 14·119 ±0·003, c 8·712±0·007 Å, β 124° 57′ ± 3′. The harmotome is Ba-poor, and 2 Na+ has substituted for Ba2+ on a valency basis. Analcime associated with the Maungarahu harmotome has chemical composition: (Na15·16 K0·03Ca0·09)Al15·52Si32·47 15·93 H2O and physical properties: n = 1·483, D = 2·257, a = 13·708 Å. The zeolites are believed to have crystallized from Na and Ba-rich alkaline solutions at approximately 200°C The source of the Ba is baryte concretions in adjacent limestones.

Khvorovite, ideally Pb42+Ca2[Si8B2(SiB)O28]F, is a new borosilicate mineral of the hyalotekite group from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, Tajikistan. Khvorovite was found in a pectolite aggregate in silexites (quartz-rich rocks). The pectolite aggregate consists mainly of pectolite, quartz and fluorite, with minor aegirine, polylithionite, turkestanite and baratovite; accessory minerals are calcite, pyrochlore-group minerals, reedmergnerite, stillwellite-(Ce), pekovite, zeravshanite, senkevichite, sokolovaite, mendeleevite-(Ce), alamosite, orlovite, leucosphenite and several unknown Cs-silicates. Khvorovite occurs as irregular grains, rarely with square or rectangular sections up to 150 μm, and grain aggregates up to 0.5 mm. Khvorovite is colourless, rarely white, transparent with a white streak, has a vitreous lustre and does not fluoresce under ultraviolet light. Cleavage and parting were not observed. Mohs hardness is 5–5.5, and khvorovite is brittle with an uneven fracture. The measured and calculated densities are 3.96(2) and 3.968 g/cm3, respectively. Khvorovite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.659(3), βcalc. = 1.671(2), γ = 1.676(3); 2Vmeas. = 64(3)°, medium dispersion: r < v. Khvorovite is triclinic, space group I1¯, a = 11.354(2), b = 10.960(2), c = 10.271(2) Å, α = 90.32(3), β = 90.00(3), γ = 90.00(3)°, V = 1278(1) Å3, Z = 2. The six strongest lines in the powder X-ray diffraction pattern [d (Å), I, (hkl)] are: 7.86, 100, (110); 7.65, 90, (101); 7.55, 90, (011); 3.81, 90, (202); 3.55, 90, (301); 2.934, 90, (312, 312). Chemical analysis by electron microprobe gave SiO2 36.98, B2O3 6.01, Y2O3 0.26, PbO 40.08, BaO 6.18, SrO 0.43, CaO 6.77, K2O 1.72, Na2O 0.41, F 0.88, O=F –0.37, sum 99.35 wt.%. The empirical formula based on 29 (O+F) a.p.f.u. is (Pb2.762+Ba0.62K0.56Na0.16)Σ4.10(Ca1.86Sr0.06Y0.04Na0.04)Σ2[Si8B2(Si1.46B0.65)Σ2.11O28](F0.71O0.29), Z = 2 , and the simplified formula is (Pb2+, Ba, K)4Ca2[Si8B2(Si,B)2O28]F. The crystal structure of khvorovite was refined to R1 = 2.89% based on 3680 observed reflections collected on a four-circle diffractometer with MoKα radiation. In the crystal structure of khvorovite, there are four [4]-coordinated Si sites occupied solely by Si with <Si–O>= 1.617 Å. The [4]-coordinated B site is occupied solely by B, with <B–O> = 1.478 Å. The [4]-coordinated T site is occupied by Si and B (Si1.46B0.54), with <T–O> = 1.605 Å; it ideally gives (SiB) a.p.f.u. The Si, B and T tetrahedra form an interrupted framework of ideal composition [Si8B2(SiB)O28]11–. The interstitial cations are Pb2+, Ba and K (minor Na) [A(11–22) sites] and Ca [M site]. The two A sites are each split into two subsites ∼0.5 Å apart and occupied by Pb2+ and Ba + K. The [8]-coordinated M site is occupied mainly by Ca, with minor Sr, Y and Na. Khvorovite is a Pb2+ analogue of hyalotekite, (Ba,Pb2+,K)4(Ca,Y)2[Si8(B,Be)2(Si,B)2O28]F and a Pb2+-, Ca-analogue of kapitsaite-(Y), (Ba,K)4(Y,Ca)2[Si8B2(B,Si)2O28]F. It is named after Pavel V. Khvorov (b. 1965), a Russian mineralogist, to honour his contribution to the study of the mineralogy of the Darai-Pioz massif.

The new mineral tennantite-(Ni), Cu6(Cu4Ni2)As4S13, has been discovered from the Luobusa Chromitite, Tibet, southwestern China. Tennantite-(Ni) occurs as anhedral grains ranging from 2 to 20 μm in size. In reflected light microscopy, tennantite-(Ni) is isotropic and appears yellow-greenish grey. Reflectance data for Commission on Ore Mineralogy wavelengths in air for tennantite-(Ni) are: 31.0 (470 nm), 29.6 (546 nm), 29.6 (589 nm) and 29.3 (650 nm). Electron microprobe analysis for holotype material gave the empirical formula (on basis of total cations = 16 apfu): M(2)Cu6 M(1)[Cu4.00(Ni0.97Cu0.53Fe0.50)Σ2.00]Σ6.00X(3)(As2.94Sb1.06)Σ4S12.77. Tennantite-(Ni) is cubic, with space group I$\bar{ 4}$3m (#217), a =10.2957(9) Å, V = 1091.4(3) Å3 and Z = 2. By using single-crystal X-ray diffraction, the crystal structure has been determined and refined to a final R1 = 0.0423 on the basis of 163 independent reflections [Fo > 4σ (Fo)]. The calculated seven strongest powder X-ray diffraction lines [d in Å (I) (hkl)] are: 2.972 (100) (222), 1.820 (83) (440), 2.574 (28) (400), 1.552 (18) (622), 3.640 (10) (220), 1.880 (10) (521) and 1.287 (7) (800). Tennantite-(Ni) is isostructural with other tetrahedrite-group minerals, and nickel is hosted at the tetrahedrally coordinated M(1) site, along with Cu and minor Fe. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2021-018).

The basic technique for preparing micro-thin rock-sections has altered little since this method of studying rocks was first accepted. Abrasive powders were, and still are, used either on glass or metal plates, the grinding being done entirely by hand. At the present time carborundum is almost universally used as the abrasive. The technique has been speeded up somewhat by the use of horizontal metal laps, and in more recent years the introduction of high-speed diamond-cutting and lapping apparatus has considerably reduced the time involved in making a thin rock-section. But even with this apparatus the process is still long and laborious, and, even more important, the operator must have considerable skill and experience in keeping the specimen whole and of uniform thickness throughout the entire operation.

Ferri-fluoro-katophorite is the second species characterised involving the rootname katophorite in the sodium–calcium subgroup of the amphibole supergroup. The mineral and its name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification, IMA2015-096. It was found in the Bear Lake diggings, Bancroft area, Ontario, Canada, where coarse euhedral crystals of amphibole, phlogopite, sanidine solid-solution (now coarsely exsolved to microcline perthite), titanite, augite, zircon and fluorapatite crystallised from a low-viscosity silicocarbonatitic magma of crustal origin. Greenish grey prismatic crystals of ferri-fluoro-katophorite generally protrude from the walls into a body of coarsely crystalline calcite, but they also occur away from the walls, completely enclosed by calcite. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(Na0.55K0.32)Σ0.87B(Na0.79Ca1.18Mn2+0.03)Σ2.00C(Mg3.29Mn2+0.02Fe2+1.19Fe3+0.31Al0.09Ti4+0.08Li0.02)Σ5.00T(Si7.39Al0.61)Σ8.00O22W[F1.23 (OH)0.77]Σ2.00. Ferri-fluoro-katophorite is biaxial (–), with α = 1.640(2), β = 1.652(2), γ = 1.658(2), 2Vmeas. = 68.9(2)° and 2Vcalc.. = 70.1°. The unit-cell parameters are a = 9.887(3), b = 18.023(9), c = 5.292(2) Å, β = 104.66(3)°, V = 912.3(6) Å3, Z = 2 and space group C2/m. The strongest ten lines in the powder X-ray pattern [d values (in Å) I (hkl)] are: 2.708, 100, (151); 2.388, 74, (131); 3.139, 72, (310); 8.449, 69, (110); 2.540, 65, ($\bar{2}$02); 2.591, 53, (061); 2.739, 47, ($\bar{3}$31); 2.165, 45, (261); 3.279, 44, ($\bar{2}$40); 2.341, 43, ($\bar{3}$51).

The Mineo pallasite is a relatively poorly known meteorite, which shows interesting features that are not fully understood, such as the occurrence of iron oxide regions bordering both the olivine grain boundaries and the (Fe,Ni) metal. In this study, the Fe oxides have been characterised by Raman spectroscopy, electron microprobe analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and 3D electron diffraction (3D ED). The combination of TEM–EDS and 3D ED yields a reliable identification of the chemical and crystallographic features of the cryptocrystalline portion of the sample investigated, enabling the Fe-oxide regions to be positively identified as goethite, FeO(OH).

The occurrence of goethite was unambiguously associated with terrestrial alteration, also confirmed by the presence of calcite, detected by TEM-EDS and 3D ED. Goethite contains minor elements such as Na, Si and Ca, probably coming from alumino-silicates in the terrestrial environment, and Ni associated with the (Fe,Ni) metal. The observation of goethite along olivine grain boundaries, as an alteration product of the (Fe,Ni) metal diagenesis, is also very intriguing as it might be related to the (Fe,Ni) metal intruded into the sub-micrometric olivine fragments during pallasite formation. Further work is needed to extensively analyse the texture and composition of olivine/metal boundaries.

Fractionation factors for the isotopes of O, H, S, or Cu (as appropriate) were determined for the minerals brochantite [Cu4(SO4)(OH)6], libethenite [Cu2(PO4)(OH)] and olivenite [Cu2(AsO4)(OH)] and corresponding aqueous solutions at temperatures between 30 and 70°C. All samples used for this determination were synthetic and the degree of fractionation was expressed as 1000 ln α = (A × 106/T2) + B, where A and B are empirical parameters. A few natural libethenite samples from its type locality Ľubietová-Podlipa were also analysed and compared to the prediction based on the isotopic composition of meteoric water and our fractionation factors. The hydrogen fractionation factors agreed with the prediction well, whereas those for oxygen did not. A possible explanation is the disequilibrium of aqueous phosphate (and also arsenate) species and the solution in our experiments or the interaction of meteoric fluids with the isotopically heavy (in terms of oxygen) country rocks. Because the effects of isotopic disequilibrium in our experiments cannot be ruled out, the oxygen fractionation factors should be used with caution. The determined fractionation factors can be used as an isotope geothermometer, given that it can be proven that the phases of interest precipitated from the same fluid in equilibrium. Libethenite is predicted to have slightly lower δ65Cu values than its parental solution, but brochantite slightly higher δ65Cu values than its parental solution. Simple forward models, simulating neutralisation or reduction of mine drainage, show that precipitation of these minerals and removal of the co-existing fluid, could cause isotopic variations (in δ65Cu) on the order of 1‰ or more.

Fluorsigaiite, ideally Ca2Sr3(PO4)3F, is a new Sr analogue of fluorphosphohedyphane and a new member of the apatite supergroup. It was discovered in lujavrite from the Saima alkaline complex, Liaoning Province, China. Fluorsigaiite commonly occurs as individual prismatic, columnar and platy crystals of 10 to 50 μm in size, associated with microcline, nepheline, aegirine, natrolite, eudialyte, fluorapatite, a fluorstrophite-like mineral, stronadelphite and calcite. Occasionally, crystals of fluorsigaiite form prismatic aggregates in the interstices of lujavrite. Fluorsigaiite is translucent to transparent, colourless to yellowish white with a vitreous lustre and without fluorescence. The estimated Mohs hardness is 5, and the tenacity is brittle with uneven fractures. The calculated density is 3.842 g/cm3. Optically, fluorsigaiite is uniaxial (–) with ω = 1.64(1) and ɛ = 1.63(1) in white light and without dispersion. The mean chemical composition (in wt.%) of fluorsigaiite is Na2O 0.75, CaO 15.17, SrO 44.44, La2O3 3.64, Ce2O3 2.22, Pr2O3 0.19, Nd2O3 0.13, Sm2O3 0.05, Gd2O3 0.23, P2O5 31.87, F 1.91, H2O 0.46, sum 100.26, giving the empirical formula (Sr2.82Ca1.79Na0.16La0.15Ce0.09Pr0.01Nd0.01Gd0.01)Σ5.04P2.97O12[F0.66(OH)0.34]Σ1, which is calculated on the basis of 13 total anions and F+(OH) = 1. The strongest eight lines of its powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.563 (15) (002), 3.275 (15) (102), 3.144 (19) (120), 2.876 (100) (121), 2.861 (96) (112), 2.772 (27) (300), 1.991 (17) (222) and 1.895 (23) (213). Fluorsigaiite is hexagonal, in the space group P63/m and unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 9.6101(2) Å, c = 7.1311(1) Å, V = 570.35(3) Å3 and Z = 2. It is isostructural with hedyphane-group minerals, and contains different prevailing (species-defining) Ca and Sr cations at the Ca1 and Ca2 sites, respectively. Fluorsigaiite was probably formed from Sr-rich fluids at late-magmatic or hydrothermal stage of the Saima lujavrite.

Of the many small manganese deposits which have in the past been worked in both Cornwall and Devonshire that of Treburland is from the mineralogical point of view by far the most remarkable, its especial interest being due to the variety of minerals which it has afforded and to the fact that it and one other are the only manganese deposits in the west of England which are known to lie on the contact of igneous and sedimentary rocks and which have consequently been vitally affected by contact metamorphism.

The following observations are based on frequent visits to the spot since the year 1906, when I first stumbled across the locality, which, strange to say, has only received very cursory mention by the Geological Survey and has altogether escaped mention in mineralogical literature.

Analytical data on a garnet-chlorite rock and the contained garnet with spectrographic determinations of the trace elements are presented, and the principles determining the distribution of these elements between the garnet and the chlorite are discussed.

The chapters of this work purport to be chronicles of the present state of our knowledge of the mineralogy of the northern portion of the kingdom. The geognosy and lithology are treated of to such an extent only as, in the first place, to explain the position of the minerals ; and, in the second, to aid future investigators in their explorations.

In these chapters, in order to do full justice to the work of others, the authority for, and the original discoverer of every locality mentioned, will be quoted, wherever known.

The author, having attempted to visit every known mineral locality to the north of the Forth and Clyde, and having succeeded in this attempt with less than half-a-dozen exceptions, is able in most cases to authenticate, or the opposite, as the case may be, the statements of previous observers.

The Tomhannock Creek chondrite has been analysed, with the following results: Fe 11·36, Ni 1·69, Co 0·07, FeS 5·26, SiO2 36·88, TiO2 0·135, Al2O3 1·80, Cr2O2 0·30, FeO 14·94, MnO 0·31, MgO 23·81, CaO 1·39, Na2O 0·73, K2O 0·095, P2O5 0·36, H2O+ 0·34, C 0·10; total 99·57. The mineralogical composition is olivine (Fo81), hypersthene (En83), plagioclase (An22), nickel-iron, troilite, chromite, and probably apatite. The density of the meteorite is 3·65.

Tomhannock Creek is not identical with Homestead, nor with Yorktown. Yorktown is a chondrite that appears to have fallen near Yorktown, Westchester County, New York (41° 17′ N., 73° 49′ W.), in September 1869.

In the first part of this paper it was shown that the acid section of the mica group could be divided into two main series, the potash micas and the lithia micas. The molecular ratio of potash to silica was 1 : 6 and the micas were therefore represented as salts of an acid characterized by this value. The present section contains the result of a similar investigation of the basic micas, especially biotite and phlogopite; here again it will be seen that the grouping K2O. 6SiO2 is present throughout. For comparison of the molecular composition, the analyses of the basic micas have been recalculated in molecular ratios, (Si,Ti)O2 being made equal to 600 according to the method already used for the acid micas.

The mineral described in this paper occurs at tile Hudson Bay zinc mine about five miles east of Saline, near Nelson in the West Kootenay district of British Columbia, I regret that I have no data as to the exact character of the ore-body except that it occurs in a region where palaeozoic rocks are intruded by biotite-granite and that it is probably genetically connected with the intrusion of the latter. The zinc occurs ill the form of the silicate and tb a less extent the carbonate. There is also a small amount of oxidized lead-ore, principally cerussite.

Earlier palaeomagnetic studies on the Dunedin volcano showed that a portion of the sequence is reversely or anomalously magnetized. Some of the rocks used for palaeomagnetic study were subsequently classified into groups according to their thermomagnetic behaviour (unpublished work).

Cell dimensions and Curie-point curves have been measured for oxides separated from representative rocks of each group. The oxides are mostly homogeneous titanomagnetites containing between 40 and 55 mol. % of ulvöspinel, with a generally small degree of late low-temperature alteration. X-ray and thermomagnetic data also suggest that there was some early oxidation to titanomaghemite, probably during cooling.

The thermomagnetic behaviour of rocks classified in the different groups is attributed to variable oxidation of the titanomagnetite during thermomagnetic treatment. The high Curie points of rocks used for palaeomagnetic studies may often be due merely to oxidation of titaniferous magnetite and not to nearly pure primary Fe3O4. Since there is insufficient oxidation in the lavas examined for any currently accepted self-reversal process to have been operative, the reversely magnetized part of the Dunedin sequence was probably erupted during a reversed polarity epoch, possibly between about 13 and 11 million years ago.

The basanitic lavas contain minor amounts of chromiferous spinel, as inclusions in silicate phenocrysts and as cores to separate microphyric titanomagnetite; its significance is briefly discussed.