Mafic rocks of the Bushveld Complex at the southeastern end of the western limb, intersected in bore core from the Cullinan Diamond Mine, are described. A 260 m thick ultramafic body of orthopyroxene and chromite cumulate rocks, with mg# – 100*Mg/(Mg+Fe) – values from 77 to 84 and 0.25 to 0.5% Cr2O3 in the pyroxene, is considered to have affinity to the Critical Zone. Such an interpretation considerably extends the eastern limit of Critical Zone rocks of the western limb of the Bushveld Complex. The whole-rock composition of the lower, chilled basal contact of this body has 10% MgO and 500 ppm Cr, and is comparable to magmas considered parental to the Bushveld Complex. Due to intrusion of a younger sill, the upper contact is not preserved in the bore core. The cumulate rocks have higher interstitial component, inferred from incompatible trace element abundances (Zr, Ti and K), than normal Critical Zone rocks, interpreted to be a result of more rapid cooling due to proximity to the basal contact. The near-constancy of mg# in the pyroxene in the entire succession suggests that large volumes of magma flowed through this conduit, with only the liquidus phases of orthopyroxene and chromite being precipitated.

Five generations of sills, intruded into the underlying metasedimentary rocks, are identified. The oldest is tholeiitic, and was metamorphosed prior to the emplacement of the Bushveld Complex. The second equates to the magma proposed as being parental to the Bushveld Complex (2060 Ma). The third represents the products of differentiation of that magma. The fourth is syenitic, and related to the Pienaars River Alkaline Complex (1430–1300 Ma). The fifth is tholeiitic (1150 Ma), and cuts the Cullinan kimberlite.

The mineralogical characteristics of halloysite in rectorite pelite in the Zhongxiang area, Hubei, China, were investigated using X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy methods. The results show that halloysite crystals exhibit euhedral lamellar, tubular or club-like, and needle-like or fibre-like morphologies, indicating that they crystallized from a significantly water-saturated environment. The mineral assemblage of the rectorite pelite is rectorite, halloysite, illite, gypsum, pyrite and rutile, suggesting a weak supergene alteration. Several features related to crystallization of halloysite were noted. Growth of halloysite on rectorite edge surfaces in voids and twins of halloysite on a nanometer scale with composition plane (110) were found in the Zhongxiang rectorite pelite, and, in particular, the tapered ends of tubes suggest that halloysite crystallized from solution. Disaggregation of lamellar halloysite particles into parallel clusters of single tubular halloysite crystals suggests that because of significant [H2O] activity in the environment, halloysite may have been derived from the alteration of rectorite.

Published electron microprobe analyses of mattheddleite, a lead sulpho-silicate apatite from Leadhills, Scotland, have 9–13% IV site deficiencies. However, galena was used as a standard for S, which suggested that low S resulted from a shift in the S-Kα peak. Wavelength scans with a PET crystal show that the S-Kα peak is shifted down by 0.0026 Å for sulphates relative to sulphides. Quantitative analyses show a ∼30% increase of S in mattheddleite using a celestite standard, which fills the IV site, but with Si > S, on average Pb5S1.2Si1.8O11.7Cl0.6(OH)0.4. Direct analysis of oxygen with the electron microprobe implies that the charge imbalance engendered from the inequality of Si and S is compensated with substitution of a vacancy (□), as in Pb5S1.2Si1.8[O11.7□0.3] [Cl0.6(OH)0.4] or Pb5S1.2Si1.8[O11.7(Cl, OH)0.73]. [Cl,OH)0.7 □0.3]. Calculation of OH as l–C1 suggests the presence of both OH- and Cl-dominant mattheddleite at Leadhills, but direct analysis of H is needed to confirm the dominance of OH in the channel site. Wavelength-dispersive analyses of S in apatite and other sulphates must be undertaken with sulphate standards: use of sulphide standards yields a negative error on the order of 10–20% in the resultant S concentration. Reactions of mattheddleite with other Pb minerals at Leadhills show that their stability depends on fluid composition as well as pressure and temperature. An X-ray map of Cl shows complex zoning between Cl-poor and Cl-rich mattheddleite, recording rapid changes in the fluid chemistry during late-stage hydrothermal processes at Leadhills.

The rare hydrous scandium phosphate, kolbeckite, [Sc(PO4).2H2O], has been recognized for the first time from the Hagendorf-Pleystein pegmatite province. The mineral was formed by the alteration of quartz-rich relict cores of pegmatites containing rutile, ilmenite, columbite, pyrochlore, wolframite, monazite and apatite. The alteration process involved acidic meteoric water and was not related to low-temperature hydrothermal fluids. Scandium and phosphorous for the formation of the kolbeckite were provided by the decomposition of the primary oxides and phosphates, respectively. Hydrous Sc phosphates are considered to form only during advanced stages of weathering in Al- and Fe-poor environments. In Al- and Fe-rich environments Sc is scavenged from solution as a trace component of Al- and Fe phosphates. A special type of leucoxene containing Fe, Al and P was formed during the process of formation of kolbeckite. In the absence of phosphate anions, Sc is removed in solution and ‘normal’ leucoxene is formed.

The prismatic variety of fluoro-edenite, a new amphibole found in lavas from Mt Etna in Biancavilla (Catania Province, Sicily, Italy), has been characterized by μ-Raman and μ-FTIR spectroscopy. The wavenumbers at which the bands are detected in the μ-Raman and μ-FTIR spectra are compared with tremolite, asbestos the chemical and crystallographic characteristics of which are very similar to those of fluoro-edenite.

A uranopilite from The South Alligator River, Northern Territory, Australia, has been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) with EDAX attachment, and thermogravimetry in conjunction with evolved gas mass spectrometry. The XRD shows that the mineral is a pure uranopilite with few if any impurities. The SEM images show that the uranopilite consists of elongated crystals, up to 50μm long and 5 μm wide. Thermogravimetry combined with mass spectrometry shows that dehydration occurs at ∼31°C resulting in the formation of metauranopilite. The first dehydration step over 20–71°C corresponds to a decrease of 5.4 wt.%, equivalent to 6.076 H2O. The second dehydration step, over the temperature range 71 –162.4°C corresponds to a decrease of 4.7 wt.%, equivalent to 5.288 H2O, making a total of 11.364 moles of H2O, close to 12 H2O for uranopilite.

Dehydroxylation takes place over the temperature range 80–160°C. The loss of sulphate occurs at higher temperatures in two steps at 622 and 636°C. A mass loss also occurs at 755°C, accounted for by evolved oxygen.

The high-temperature (HT) behaviour of kyanite (Al2SiO5) was investigated by in situ neutron powder diffraction up to 1200°C. Within the investigated T range, no phase transition was observed. The axial and volume thermal expansion coefficient (αj = lj-1(𝜕1j/𝜕T), αv = V-1 (𝜕V/𝜕T)), calculated by weighted linear regression through the data points, are: αa = 5.5(2) x 10-5, αb= 5.9(2) x 10-5, αc = 5.18(8) xl0-5, αv = 7.4(1) x 10-3 “C-1, with αa:αb:αc = 1.06:1.14:1. All three angles of the kyanite lattice show a slight decrease with T, with 𝜕α/𝜕T = -2(2) x 10-5, 𝜕β/𝜕T = -4(1) x 10-5, 𝜕γ/𝜕T = –10(2) x 10-5%C. The magnitudes of the principal Lagrangian unit-strain coefficients (ε1,ε2, ε3) and the orientations of the thermal strain-ellipsoids, between the ambient temperature and each measured T, were calculated. The magnitude and the orientation of all the three unit-strain coefficients are almost maintained constant with T. At T-To = 1177°C , ε^a = 76(2)°, ε^b = 70(2)°, ε^c = 38(3)°, ε2^a = 49(3)°, ε2^b = 66(3)°, ε2^c = 127(4)°, ε3^a = 135(3)°, ε3^b = 31(3)°, ε3^c = 91(2)° with ε1:ε2:ε3 = 1.57:1.29:1. The structural refinements, performed at 23, 600, 650, 700, 750, 800, 900, 950, 1050 and 1200°C allowed the description of the structural evolution and the main T-induced deformation mechanisms, which are mainly represented by the polyhedral distortions of the AlO6 octahedra.

Structural modifications as a function of the degree of order (Q) in FeTa2O6 ferrotapiolite have been characterized by means of single-crystal X-ray diffraction (SC-XRD). A total of 26 datasets covering the range of Q between 0.154 and 1 have been obtained by thermal treatments followed by quenching of natural tapiolite crystals. Ordering of Fe2+ at the A sites and of Ta5+ at the B sites causes a linear increase in the a/c lattice constants ratio, as a consequence of a linear decrease of the c dimension and only slight modifications of the a parameter. Calibration of a/c vs. Q represents a very useful tool for a rapid determination of the degree of order of tapiolite samples. Polyhedral volumes of the two octahedral sites vary linearly with Q as a consequence of the different ionic radii of the two species. Both the sites remain almost regular at all Q values but the B site shows an increasing off-centre displacement of the cation with increasing Q. Observed structure factors of supercell reflections, characterized by l ≠ 3n, increase linearly as a function of Q, thus representing a further tool for a quick evaluation of the degree of order.

Kapellasite, Cu3Zn(OH)6Cl2, is a new secondary mineral from the Sounion No. 19 mine, Kamariza, Lavrion, Greece. It is a polymorph of herbertsmithite. Kapellasite forms crusts and small aggregates up to 0.5 mm, composed of bladed or needle-like indistinct crystals up to 0.2 mm long. The colour is green-blue, the streak is light green-blue. There is a good cleavage parallel to ﹛0001﹜. Kapellasite is uniaxial negative, ω = 1.80(1), ε = 1.76(1); pleochroism is distinct, with E = pale green, O = green-blue. Dmeas = 3.55(10) g/cm3; Dcalc. = 3.62 g/cm3. Electron microprobe analyses of the type material gave CuO 58.86, ZnO 13.92, NiO 0.03, CoO 0.03, Fe2O3 0.04, Cl 16.70, H2O (calc.) 12.22, total 101.80, less O = Cl 3.77, total 98.03 wt.%. The empirical formula is (Cu3.24Zn0.75)Σ3.99(OH)5.94Cl2.06, based on 8 anions. The five strongest XRD lines are [d in Å (I/I0, hkl)] 5.730 (100, 001), 2.865 (11, 002), 2.730 (4, 200), 2.464 (9, 021/201), 1.976 (5, 022/202). Kapellasite is trigonal, space group Pml, unit-cell parameters (from single-crystal data) a = 6.300(1), c = 5.733(1) Å, V= 197.06(6) Å3, Z = 1. The crystal structure of kapellasite is based on brucite-like sheets parallel to (0001), built from edge-sharing distorted M(OH,Cl)6 (M = Cu, Zn) octahedra. The sheets stack directly on each other (…AAA… stacking). Bonding between adjacent sheets is only due to weak hydrogen and O…C1 bonds. The name is in honour of Christo Kapellas (1938–2004), collector and mineral dealer from Kamariza, Lavrion, Greece.