Bystrite is redefined as a four-layer cancrinite-group mineral with the four-layer Losod-type framework and the end-member formula Na7Ca(Al6Si6O24)S52–Cl–. The mineral is known only at the Malo–Bystrinskoe gem lazurite deposit, Baikal Lake area, Siberia, Russia. The associated minerals are calcite, lazurite, sodalite, fluorapatite, phlogopite, diopside, dolomite and plagioclase. Bystrite is brittle, with the Mohs hardness of 5 and distinct cleavage on {10$\bar{1}$0}. The yellow colour of bystrite is due to the presence of S52– anions occurring in Losod (LOS) cages of the aluminosilicate framework with the ABAC stacking sequence. Measured and calculated density is, respectively, 2.43(1) and 2.412 g cm–3 for the holotype and 2.42(1) and 2.428 g cm–3 for the cotype sample. Bystrite is uniaxial (+), ɛ = 1.660(2) and ω = 1.584(2). The mineral was characterised by infrared and Raman spectra. The empirical formulae of the holotype and cotype samples are Na6.97K0.04Ca0.98(Si6.03Al5.97O24)(S52–)0.93[(SO42–)0.15Cl0.83] and Na6.75K0.04Ca1.11(Si6.09Al5.91O24)(S52–)1.04[(HS–)0.17Cl0.85], respectively. Bystrite is trigonal, space group P31c. The unit-cell parameters are: a = 12.8527(6) Å, c = 10.6907(5) Å, V = 1529.4(1) Å3 and Z = 2. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 4.821 (32) (102), 3.915 (38) (211), 3.712 (100) (300), 3.307 (50) (212), 2.782 (18) (400), 2.692 (22) (401), 2.673 (30) (004) and 2.468 (23) (402). Isomorphism and genesis of bystrite-type minerals is discussed. Bystrite and its K,HS-analogue sulfhydrylbystrite, Na5K2Ca(Al6Si6O24)S52–(HS)–, are indicators of highly reducing conditions.

Intermediate-level radioactive waste is normally encapsulated in cementitious grout. However, for some wastes, grout may not be suitable and polymeric encapsulants are being considered as an alternative. One concern with such encapsulants is their long-term chemical stability and the possibility that release of aggressive degradation products could cause corrosion.

This paper evaluates the potential for three polymeric encapsulants: two epoxy resins (the APS polymer system, (APS) and Alchemix 4760 (ALC)) and a vinyl-ester styrene (VES); to cause internal corrosion of stainless steel waste containers. The corrosion behaviour of stainless steel 316L in contact with each encapsulant was studied in saturated Ca(OH)2 solutions and deionized (DI) water, at 80°C, under non-irradiated and γ-irradiated conditions.

In aerated, alkaline conditions, 316L was resistant to corrosion in all the conditions tested. However, in DI water, the pH fell to values as low as three due to release of acidic species from the polymers. The two epoxy materials (particularly APS) also released significant levels of chloride; VES did not. Chloride release appeared to be increased by γ-irradiation. As a result of the low pH chloride-containing environment created by the APS encapsulant, 316L experienced localized corrosion, whereas coupons in Alchemix 4760 and VES did not. Weight loss measurements correlated with visual observations. γ-irradiation appeared to increase the degree of corrosion.

Structural data for weishanite, an alloy of Au, Ag and Hg, were collected for the first time from a crystal from the Keystone Mine, Colorado, USA. The structure was solved in the space group P63/mmc with the unit cell a = 2.9348(8) and c = 4.8215(18) Å] and refined to R = 0.0299 for 40 observed reflections [4σ(F) level] and four parameters and to R = 0.0356 for all 47 independent reflections. The weishanite structure can be considered a derivative of the zinc structure, with Au, Ag and Hg disordered in the same structural position. On this basis, we suggest that the formula is normalized to 1 atom with Z = 2, leading, for the sample investigated, to Au0.41Ag0.31Hg0.28 (electron microprobe data). Accordingly, weishanite can be considered the Au-rich isotype of schachnerite. A comparison with other Au/Ag-Hg alloys is presented together with a critical discussion about the nomenclature rules to be applied to alloys and simple metals.

By the publication of his paper on 'The source of the purple zircons in the sedimentary rocks of Scotland', Dr. Wm. Mackie has done his fellow-workers on the petrology of British sedimentary rocks a signal service, He has proved that this distinctive purple (or sometimes rosecoloured) variety of zircon is relatively abundant in the Lewisian gneiss. The variety occurs usually as rounded or ovoid grains, but occasionally with crystalline form ; it is often finely polished, as if by wind, and is sometimes zoned, with a darker centre, or displays colour of varying intensity; it is often definitely, although but slightly, pleochroic, and usually possesses high bireffingence. These characteristics at once bring to mind grains of zircon frequently met with in sedimentary rocks and recorded by numerous other observers.

Mr. Arthur Russell collected in 1930 on Pim Hill, near the village of Harmer Hill, 6 miles north of Shrewsbury, Shropshire, specimens of Triassic sandstone encrusted with minute black crystals. They resemble very closely the material from Mottram St. Andrew, Cheshire, which was described and named mottramitc by Sir Henry E. Roscoe in 1876.1 Mr. Russell pointed out this resemblance and kindly placed his specimens of this rare British mineral at our disposal for investigation.

In a recent paper by Dr. W. F. Fleet and Dr. F. Smithson attention was drawn, to the occurrence of dark apatites and apatitcs with dark cores of inclusions in certain sediments of the Midlands of England, and it was pointed out that the only other definite occurrences known of these peculiar apatite grains in either igneous or sedimentary rocks appeared to be restricted to the Old Red Sandstone of the Cardiff area, the ‘newer’ granites of Jersey, and the Leinster granite. These writers also expressed the hope ‘that any future observation of such grains may be recorded with a view to tracing the source of the detrital grains of Welsh and English rocks’.

The three varieties of apatite at present known to occur in Cornwall are the sea-green limpid crystals from St. Michael's Mount and other places, the dirty-white, semi-opaque, hexagonal prisms associated with axinite from Botallack Head, and the thin hexagonal plates, described and analysed by Prof. Maskelyne and Dr. Flight as coming from a new locality, now known, however, to have been obtained by the late Mr. Tailing from Fowey Consols, and previously noted from this mine by Greg and Lettsom. To these must now be added a new variety which was lately brought to me as chalybite from the deep workings of Levant Mine, St. Just. The specimens are closely analogous to those analysed by Dr. Flight, but differ slightly in chemical composition and mode of occurrence.

The recently defined arctite supergroup contains nine mineral members defined as hexagonal intercalated antiperovskites, most of which have been found in pyrometamorphic rocks of the Hatrurim Complex, Israel. Three members of this supergroup: nabimusaite, gazeevite and zadovite, were identified for the first time in altered carbonate–silicate xenoliths from the Caspar and Scherer quarries, Bellerberg volcano in Germany. Present work focuses on the chemical, structural and spectroscopic investigation of these minerals and their correlation with holotype counterparts. The apparent differences are mainly related to the chemical composition, types of substitution in the tetrahedral and antiperovskite layers within the crystal structure, and position of bands in the Raman spectra. In the Bellerberg volcano xenoliths, the crystallisation of nabimusaite and gazeevite is caused by high-temperature alteration of early mineral associations (clinker-like phases) and their reaction with melt or gas generated by volcanic activity. In turn, the formation of zadovite is related to the Ba-rich silicate melt that filled the intergranular space between the rock-forming minerals.

The new mineral somersetite, has been found at Torr Works (‘Merehead quarry’) in Somerset, England, United Kingdom. Somersetite is green or white (typically it is similar visually to hydrocerussite-like minerals but with a mint-green tint), forms plates and subhedral grains up to 5 mm across and up to 2 mm thick. In bi-coloured crystals it forms very thin intergrowths with plumbonacrite. The empirical formula of somersetite is Pb8.00C5.00H4.00O20. The simplified formula is Pb8O(OH)4(CO3)5, which requires: PbO = 87.46, CO2 = 10.78, H2O = 1.76, total 100.00 wt.%.

The infrared spectrum of somersetite is similar to that of plumbonacrite and, to a lesser degree, hydrocerussite. Somersetite is hexagonal, P63/mmc, a = 5.2427(7), c = 40.624(6) Å, V = 967.0(3) Å3 and Z = 2. The eight strongest reflections of the powder X-ray diffraction (XRD) pattern [d,Å(I)(hkl)] are: 4.308(33)(103), 4.148(25)(104), 3.581(40)(107), 3.390(100)(108), 3.206(55)(109), 2.625(78)(110), 2.544(98)(0.0.16) and 2.119(27)(1.0.17). The crystal structure was solved from single-crystal XRD data giving R1 = 0.031. The structure of somersetite is unique and consists of the alternation of the electroneutral plumbonacrite-type [Pb5O(OH)2(CO3)3]0 and hydrocerussite-type [Pb3(OH)2(CO3)2]0 blocks separated by stereochemically active lone electron pairs on Pb2+. There are two blocks of each type per unit cell in the structure, which corresponds to the formula [Pb5O(OH)2(CO3)3][Pb3(OH)2(CO3)2] or Pb8O(OH)4(CO3)5 in a simplified representation. The 2D blocks are held together by weak Pb–O bonds and weak interactions between lone pairs.

Maneckiite, ideally NaCa2Fe22þ (Fe3+Mg)Mn2(PO4)6(H2O)2, was found in a pegmatite at Michałkowa, Góry Sowie Block, SW Poland. The mineral forms subhedral and anhedral crystals ~150 μm × 150 μm in the outer zone of phosphate nodules, where it is associated with fluorapatite, wolfeite, Ca-rich graftonite and alluaudite-group minerals. Maneckiite is transparent, dark brown, with a colourless streak and vitreous lustre, brittle, and has a good cleavage // {010}, a splintery fracture and a Mohs hardness of ~5. The calculated density is 3.531 g cm–3. Maneckiite is pleochroic: α = dark green, β = dark blue/green, γ = light brown/tan, biaxial (+) with refractive indices α = 1.698(2), β = 1.706(2), γ = 1.727(2) and birefringence Δ = ~0.03; 2Vmeas. = 65.9 (1.5)° and 2Vcalc. = 64°, dispersion is obscured by the dark colour, and optical orientation X//a, Y//b, Z//c. Maneckite is orthorhombic (Pcab) and has unit-cell parameters a = 12.526(4) Å, b = 12.914(5) Å, c = 11.664(4) Å and V = 1886.8(5) Å3. The strongest reflections are (dhkl in Å; I; hkl): 2.759, 100, 402; 2.916, 78, 004; 3.020, 68, 401; 2.844, 35, 014; 2.869, 31, 240; 2.825, 30, 042. Maneckiite has the wicksite structure and is its M(3)Mn-analogue. The mineral crystallized as a product of Na- and Ca-metasomatism induced by a HT fluid in the presence of Al3+ from a neighbouring aluminosilicate melt. A Gladstone-Dale index, 0.027, places maneckiite in the category ‘excellent’.

Galeaclolusite, [Al6(AsO4)3(OH)9(H2O)4]⋅8H2O, is a new secondary hydrated aluminium arsenate mineral from Cap Garonne, Var, France. It forms crusts and spheroids of white fibres up to 50 μm long by 0.4 μm wide and only 0.1 μm thick. The fibres are elongated along [001] and flattened on (100). The calculated density is 2.27 g⋅cm–3. Optically, galeaclolusite is biaxial with α = 1.550(5), β not determined, γ = 1.570(5) (white light) and partial orientation: Z = c (fibre axis). Electron microprobe analyses coupled with crystal structure refinement results gives an empirical formula based on 33 O atoms of Al5.72Si0.08As2.88O33H34.12. Galeaclolusite is orthorhombic, Pnma, with a = 19.855(4), b = 17.6933(11), c = 7.7799(5) Å, V = 2733.0(7) Å3 and Z = 4. The crystal structure of galeaclolusite was established from its close relationship to bulachite and refined using synchrotron powder X-ray diffraction data. It is based on heteropolyhedral layers, parallel to (100), of composition Al6(AsO4)3(OH)9(H2O)4 and with H-bonded H2O between the layers. The layers contain [001] spiral chains of edge-shared octahedra, decorated with corner-connected AsO4 tetrahedra, that are the same as in the mineral liskeardite.

The crystal structure of chenevixite, Cu2M2(AsO4)2(OH)4 (where M = Fe3+ or Al), pseudo-orthorhombic, monoclinic, a = 5.7012(8), b = 5.1801(7), c = 29.265(2) Å, β = 89.99(1)°, V = 864.3(4) Å3, space group B1211, Z = 4, was solved by direct methods and refined by least-squares techniques to R = 8.4% and a goodness-of-fit (S) of 1.37 for 1176 unique observed (F≥4σF) reflections collected for a twinned microcrystal using graphite-monochromated Mo-Kα X-rays and a CCD area detector. Vertex- and edge-sharing arsenate tetrahedra, Alϕ6 octahedra, and Jahn-Teller-distorted Cu2+ϕ6 octahedra [ϕ: O2−;, (OH)−;] form a framework unique from those in Cu2+ oxysalt minerals. Chains of edge-sharing Cu2+ϕ6 octahedra, with Alϕ6 octahedra attached on opposing sides by the sharing of edges, are linked into layers parallel to (001) by sharing vertices with AsO4 tetrahedra, and the layers are linked to form a frameworkby the sharing of polyhedral elements between adjacent Alϕ6 octahedra, as well as between AsO4 tetrahedra and Alϕ6 octahedra.

Marshallsussmanite (IMA2013-067) is a new pyroxenoid mineral from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Marshallsussmanite has ideal formula NaCaMnSi3O8(OH) and triclinic P$\bar{1}$ symmetry. Marshallsussmanite forms vitreous pink bladed crystals to 2.1 cm. The mineral shows perfect cleavage on both {100} and {001}. The chemical composition from electron microprobe (average of 20 analyses) and inductively coupled plasma mass spectrometer analysis (average of three analyses) is Li2O 0.43, Na2O 8.06, MgO 0.08, CaO 15.33, MnO 21.79, SiO2 51.71; totalling 97.40 wt.%. The empirical formula, normalized to 3 Si and assuming 1 H apfu is Li0.100Na0.906Ca0.953Mg0.007Mn1.071Si3O8(OH). Unit-cell parameters from single crystal X-ray diffraction are a = 7.7854(4), b = 6.9374(4), c = 6.8516(3) Å, α = 90.683(3)°, β = 94.330(3)°, γ = 102.856(3)°, V = 359.59(3) Å3; Z = 2. The crystal structure refinement converged with Robs = 0.0248 and site occupancy refinement gives crystal chemistry [Na0.948Li0.052][Ca0.793Mn0.207] [Mn0.937Ca0.063]Si3O8(OH). Marshallsussmanite is a single chain silicate with a repeat interval of three tetrahedra (i.e. dreier chain). Marshallsussmanite is a member of the pectolite group of pyroxenoids, which also includes barrydawsonite-(Y), cascandite, pectolite, serandite and tanohataite. Parallel silicate chains form layers, intercalated with well-ordered cation layers. Calcium and Mn both exhibit octahedral coordination, while Na has four bonded interactions in a coordination sphere (radius 3 Å) of seven separate O atoms. Procrystal electron density and bond valence modelling results are compared. The mineral has an unusually strong hydrogen bond with O4⋅⋅⋅O3 separation of 2.458(2) Å. Unlike pectolite and serandite, O4 in marshallsussmanite acts as an H-bond donor and O3 is an H-bond acceptor. Cation ordering in pyroxenoids has a substantial impact on the H position and corresponding H-bonding schemata.

Nolzeite, Na(Mn,□)2[Si3(B,Si)O9(OH)2]·2H2O, is a new mineral found in altered sodalite syenite at the Poudrette quarry, La Vallée-du-Richelieu, Montérégie (formerly Rouville County), Québec, Canada. Crystals are colourless to pale green and are acicular with average dimensions of 5 μm × 8 μm × 55 μm. They occur as radiating to loose, randomly oriented groupings within vugs associated with aegirine, nepheline, sodalite, eudialyte-group minerals, analcime, natron, pyrrhotite, catapleiite, steedeite and the unidentified mineral, UK80. Nolzeite is non-pleochroic, biaxial, with nmin = 1.616(2) and nmax = 1.636(2) and has a positive elongation. The average of six chemical analyses gave the empirical formula: Na1.04(Mn1.69□0.24Fe0.05Ca0.02)∑=2.00(Si2.96S0.04)∑=3.00(B0.70Si0.30)∑=1.00O9(OH)2·2H2O based on 13 anions. The Raman spectrum shows six distinct bands occurring at ∼3600–3300 cm–1 and 1600–1500 cm–1 (O–H and H–O–H bending), 1300–1200 cm–1 (B–OH bending), 1030–800 cm–1 (Si–O–Si stretching) as well as 700–500 cm–1 and 400–50 cm–1 (Mn–O and Na–O bonding, respectively). The FTIR spectrum for nolzeite shows bands at ∼2800 –3600 cm–1(O–H) stretching, a moderately sharp band at 1631 cm –1(H–O–H) bending, strong, sharp bands at ∼650 –700 cm–1, ∼800 –840 cm–1, and ∼900–1100 cm–1(Si–O and B –O) bonds. Nolzeite is triclinic, crystallizing in space group P with a = 6.894(1), b = 7.632(2), c = 11.017(2) Å, α= 108.39(3), β= 99.03, γ = 103.05(3)°, V = 519.27 Å3, and Z = 2. The crystal structure was refined to R = 12.37% and wR2 = 31.07% for 1361 reflections (Fo > 4σFo). It is based on chains of tetrahedra with a periodicity of three (i.e. a dreier chain) consisting of three symmetrically independent SiO4 tetrahedra forming C-shaped clusters closed by BO2(OH)2 tetrahedra, producing single loop-branched dreier borosilicate chains. The chains are linked through shared corners to double chains of edge-sharing MnO5(OH) octahedra. Nolzeite is a chain silicate closely related to steedeite and members of the sérandite–pectolite series. Paragenetically, nolzeite is late-stage, probably forming under alkaline conditions and over a narrow range of low pressures and temperatures.

In the manganesiferous ores associated with the metacherts of the ophiolitic sequences at the Cerchiara mine, Eastern Liguria (Italy), a new Mn-bearing mineral belonging to the mica group has been recently found and characterized. High resolution transmission electron microscopy and electron diffraction tomography studies confirm that the mineral belongs to the mica group. Unit-cell parameters from the powder diffraction pattern are: a = 5.149(1), b = 8.915(1), c = 10.304(1) Å, β = 102.03(1)°, space group C2 or C2/m. On the basis of the electron paramagnetic resonance spectroscopic results, the Mn4+ content represents a very subordinate fraction of the total Mn, the remaining occurring as Mn3+. The Raman spectrum clearly indicates the presence of OH groups in the structure. Laser-ablation inductively-coupled-plasma mass-spectrometry measurements assess the presence of considerable amounts of Li.

Assuming all Mn as Mn3+ and 22 negative charges, the empirical formula can be expressed as: (K0.83□0.17)(Mn1.143+Mg0.80Li0.20Fe0.023+)(Si3.89Al0.10)O10[(OH)1.92F0.08] with the sum of the octahedral cations indicating a 'transitional' character between a di- and a tri-octahedral structure. This formula corresponds ideally to the Mn3+ analogue of celadonite, thus expanding the range of solid solution in the celadonite family. The ideal end-member formula KMn3+MgSi4O10(OH)2 can be easily related to celadonite by the homovalent substitution VIMn3+ → VIFe3+. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, (IMA 2015-052).

Calciodelrioite, ideally Ca(VO3)2(H2O)4, is a new mineral (IMA 2012-031) from the uraniumvanadium deposits of the eastern Colorado Plateau in the USA. The type locality is the West Sunday mine, Slick Rock district, San Miguel County, Colorado.The new mineral occurs on fracture surfaces in corvusite- and montroseite-impregnated sandstone and forms as a result of the oxidative alteration of these phases. At the West Sunday mine, calciodelrioite is associated with celestine, gypsum, huemulite, metarossite, pascoite and rossite. Themineral occurs as transparent colourless needles, bundles of tan to brown needles and star bursts of nearly black broad blades composed of tightly intergrown needles. Crystals are elongate and striated parallel to [100], exhibiting the prismatic forms {001} and {011} and having terminationspossibly composed of the forms {100} and {61}. The mineral is transparent and has a white streak, subadamantine lustre, Mohs hardness of about 2½, brittle tenacity, irregular to splintery fracture, one perfect cleavage on {001} and possibly one or more additional cleavages parallel to [100].Calciodelrioite is soluble in water. The calculated density is 2.451 g cm– 3. It is optically biaxial (+) with α = 1.733(3), β = 1.775(3), γ = 1.825(3) (white light), 2Vmeas = 87.3(9)° and 2Vcalc = 87°. The optical orientationis X = b; Z ≈ a. No pleochroism was observed. Electronmicroprobe analyses of two calciodelrioite samples and type delrioite provided the empirical formulae (Ca0.88Sr0.07Na0.04K0.01)Σ1.00(V1.00O3)2(H2.01O)4,(Ca0.76Sr0.21Na0.01)Σ0.98(V1.00O3)2(H2.01O)4 and (Sr0.67Ca0.32)Σ0.99(V1.00O3)2(H2.00O)4, respectively.Calciodelrioite is monoclinic, I2/a, with unit-cell parameters a = 14.6389(10), b = 6.9591(4), c = 17.052(2) Å, β = 102.568(9)°, V = 1695.5(3) Å3 and Z = 8. The seven strongest lines in the X-ray powder diffractionpattern [listed as dobs Å (I)(hkl)] are as follows: 6.450(100)(011); 4.350(16)(013); 3.489(18)(020); 3.215(17)(022); 3.027(50)(multiple); 2.560(28)(15,413); 1.786(18)(028). In the structure of calciodelrioite (refined to R1 = 3.14% for1216 Fo > 4σF), V5+O5 polyhedra link by sharing edges to form a zigzag divanadate [VO3] chain along a, similar to that in the structure of rossite. The chains are linked via bonds to Ca atoms, which also bond to H2Ogroups, yielding CaO3(H2O)6 polyhedra. The Ca polyhedra form a chain along b. Each of the two symmetrically independent VO5 polyhedra has two short vanadyl bonds and three long equatorial bonds. Calciodelrioite and delrioite are isostructuraland are the endmembers of the series Ca(VO3)2(H2O)4–Sr(VO3)2(H2O)4. Calciodelrioite is dimorphous with rossite, which has a similar structure; however, the smaller 8-coordinate Ca site in rossitedoes not accommodate Sr.

Holtite, approximately (Al,Ta,□)Al6(BO3)(Si,Sb3+,As3+)Σ3O12(O,OH,□s)Σ3, is a member of the dumortierite group that has been found in pegmatite, or alluvial deposits derived from pegmatite, at three localities: Greenbushes, Western Australia; Voron'i Tundry, Kola Peninsula, Russia; and Szklary. Lower Silesia, Poland. Holtite can contain >30 wt.% Sb2O3, As2O3, Ta2O5, Nb2O5, and TiO2 (taken together), but none of these constituents is dominant at a crystallographic site, which raises the question whether this mineral is distinct from dumortierite. The crystal structures of four samples from the three localities have been refined to R1 = 0.02—0.05. The results show dominantly: Al, Ta, and vacancies at the Al(l) position; Al and vacancies at the Al(2), (3) and (4) sites; Si and vacancies at the Si positions; and Sb, As and vacancies at the Sb sites for both Sb-poor (holtite I) and Sb-rich (holtite II) specimens. Although charge-balance calculations based on our single-crystal structure refinements suggest that essentially no water is present, Fourier transform infrared spectra confirm that some OH is present in the three samples that could be measured. By analogy with dumortierite, the largest peak at 3505-3490 cm-1 is identified with OH at the O(2) and O(7) positions. The single-crystal X-ray refinements and FTIR results suggest the following general formula for holtite: Al7-[5x+y+z]/3 (Ta,Nb)x□[2x+y+z]\3,BSi3-y(Sb,As)yO18-y-z(OH)z, where x is the total number of pentavalent cations, y is the total amount of Sb + As, and z ⩽ y is the total amount of OH. Comparison with the electron microprobe compositions suggests the following approximate general formulae Al5.83(Ta,Nb)0.50□0.67BSi2.50(Sb,As)0.50O17.00(OH)0.50 and Al5.92(Ta,Nb)0.25□0.83BSi2.00(Sb,As)1.00O16.00(OH)1.00 for holtite I and holtite II respectively. However, the crystal structure refinements do not indicate a fundamental difference in cation ordering that might serve as a criterion for recognizing the two holtites as distinct species, and anion compositions are also not sufficiently different. Moreover, available analyses suggest the possibility of a continuum in the Si/(Sb + As) ratio between holtite I and dumortierite, and at least a partial continuum between holtite I and holtite II. We recommend that use of the terms holtite I and holtite II be discontinued.

To date, Fe-Li micas have been defined differently from other micas. The purpose of this paper is to reinterpret the actual Fe-Li mica series with new concepts of ‘essential replacement’ (the evolution direction) and ‘composition track’ (the sequence of mica varieties). Two hundred and fifty-eight analyses from the literature are used for this study in the form of eight data groups. The common compositional and substitutional characters of Fe-Li micas have been reinterpreted in light of principal component analysis and a geometric frame of ideal Fe2+-Al-Li micas in space with (Si, AlIV, AlVI, Fe2+, Li, ☐VI, K)-coordinates.

In our new interpretation, the actual Fe-Li micas are essentially neither AlIV- nor AlVI-, but ☐VI-constant. The actual Fe-Li micas are the weakest fluctuant relative to the Annite-Polylithionite-Trilithionite-Siderophyllite (APTE) plane. About 90% of variations of actual Fe-Li micas range from the trioctahedral trend described as a sequence along the segment K2Al2Fe5/22+Li☐1/2Si6Al2O20(OH,F)4+x[AlFe−22+Li3SiAl−2] (−1/3≤ x≤5/8). The substitution AlFe−22+Li3SiAl−2 (i.e. 2AlIV +4Fe2+ → 2Si +AlVI +3Li) is the main mechanism that keeps actual Fe-Li micas trioctahedral. More than 8% of variations arise from the dioctahedral trend involving created AlVI- and ☐VI-increasing replacement. The actual Fe-Li mica series comprises the composition trend from Fe2+-biotite to lepidolite. This series is not on the siderophyllite-polylithionite join, but can be expressed ideally as K2Al1+xFe4−4x2+Li1+3x(Si6+2xAl2−2x) O20(OH,F)4 (−1/3 ≤x≤1).

Orthopyroxene and clinopyroxene, with biotite, are widespread in the high-level Cheviot granite, while amphibole is rare. The pyroxene compositions are very close to (Mg,Fe)2Si2O6 and Ca(Mg,Fe)Si2O6. Biotite compositions, with low Si and Al, are characteristic of biotites coexisting with pyroxenes. Geothermometric estimates based on oxide and pyroxene compositions show that present mineral compositions result from post-consolidation equilibration.