Detailed chemical analyses of different portions of laboratory-grown sector-zoned clinopyroxene been provided by Skulski et al. (1994). These data have been plotted here in PC-IR diagrams results indicate equilibrium crystallization and protosite control of element selection.

Single crystals of Sr feldspar (SrAl2Si2O8, space group: I2/c) were treated isothermally in the temperature range between 1410 and 1640°C, in order to determinate the evolution of the Al,Si configurations at equilibrium with thermal treatments. X-ray intensity data collection and structural refinement were performed on the quenched crystals. Significant modifications were observed in the average tetrahedral distances and therefore in Qod values.

Two different series of thermal treatments were performed: (1) a crystal of ordered Sr feldspar (Qod= 0.85) was progressively disordered at 1560°C (Qod = 0.82), at 1610°C (Qod = 0.74) and at 1640°C (Qod = 0.69); (2) another crystal with Qod = 0.72 (obtained by annealing a glass at T =1625°C), was ordered at T = 1600° (Qod = 0.75).

As already observed in anorthite quenched from 1530°C (Qod = 0.78), also in Sr feldspar, annealing near Tmelt, caused significant disorder in the Al-Si configuration (Qod = 0.69).

Observations by transmission electron microscopy show an increase in the average size of the i-type antiphase domains up to 5000Å in the samples quenched from 1640°C, in comparison with samples annealed at 1450°C (∼ 2000 Å). The modifications observed in the Al,Si configurations are due to intradomain disorder.

Rock samples from the various metabasic hornfelses of the Land's End granite aureole were analysed for major elements by X-ray fluorescence analysis and for rare-earth elements (REE) by instrumental neutron activation analysis (INAA). The REE patterns of the unaltered dolerites of the area seem to be analogous to those of the alkali basalts, taking into account a slight mobilization of the light REE during low-grade metamorphism.

The REE content of the metabasic rocks of the aureole has increased relative to that of the unaltered dolerites due to the introduction of REE, along with K, from the granite by the action of hydrothermal solutions. The parallel increase in REE with the increase in K is demonstrated.

The metasomatic hornfelses of igneous origin form two groups showing slightly different REE patterns and different rates of increase in REE content. The REE patterns of the two groups show a Eu anomaly increasing with the increase in REE content for the first group and decreasing with the increase in REE content for the second group, A qualitative model of the distribution of the REE in the metabasic aureole rocks is given.

Studies of the U decay series (238U-234U-230Th) have been carried out on samples from unaltered bedrock and highly altered fracture/crush zones from drillcore Km3 (Kamlunge test-site). The fracture zones are characterized by abundant iron oxide coatings (hematite and hydroxy iron oxides) resulting from the passage of hydrothermal solutions coeval with the Lina granite intrusion. Enrichments of U and Th, thought to be due to co-precipitation (or preferential sorption) processes together with the iron-oxides, are also present.

The isotopic results show that out of a total of twelve rock samples measured, six indicate isotopic disequilibrium mostly due to unequal depletions of 234U and 238U; one near-surface sample indicated some minor assimilation of U. The major fracture zones generally indicate removal of total U. This has resulted from interaction with groundwaters which are still marginally oxidizing, even at depths of 375 m.

Isotopic disequilibrium has occurred within recent geological times, i.e. during the last 0.5 Ma as imposed by the half-lives of 234U and 230Th. In terms of radioactive disposal considerations, the results are important in that: (1) the investigated bedrock environment (100–500 m) is generally reducing; however (2) there is some evidence to indicate that rock/water interactions, leading to the removal of total U, have resulted from the presence of less reducing groundwaters within those large-scale fracture/crush zones which intersect the bedrock surface.

Aldermanite from Tom's quarry in the Kapunda–Angaston area of the Mount Lofty Ranges, South Australia has been characterised by electron microprobe analyses and single-crystal structure analysis. The empirical formula is Na0.72K0.13Ca0.06Mg1.15Al2.92(PO4)2.05[(OH)2.92F2.96]Σ5.88⋅8.91H2O, based on 23 anions. Analysis of a specimen from the type locality, the nearby Klemm's quarry, Moculta, gave a similar formula, Na0.59K0.06Ca0.36Mg0.92Al3.16(PO4)1.97[(OH)4.08F2.70]Σ6.78⋅8.36H2O. Na and F were not analysed in the original description of the mineral. The ideal end-member formula is [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH)6]⋅H2O, compared to the original formula of Mg5Al12(PO4)8(OH)22⋅nH2O with n ≈ 32. Aldermanite is monoclinic, P21/c with a = 13.524(3), b = 9.958(2), c = 7.013(1) Å and β = 97.40(3)°. The crystal structure of aldermanite is built from sawtooth layers of cis- and trans-corner-connected, Al-centred octahedra, decorated with corner-connected PO4 tetrahedra to give (100) layers of composition Al3(PO4)2(OH,F)6. Interlayer Mg(H2O)6 octahedra and H2O molecules hold the layers together through H bonding. The corner-connected octahedra form 6-membered rings that are centred by 8-coordinated Na and have a topology identical to a 3-octahedra-wide {110} slice of the pyrochlore structure. This pyrochlore element contains intersecting kagomé nets of Al atoms, parallel to (111) and (11$\bar{1}$) of cubic pyrochlore. Minerals of the walentaite group, as well as zirconolite-3O polytypes have the same type of intersecting kagomé nets of small cations.

Yugawaralites from two localities in Japan consist of growth sectors with variable 2V values and extinction angles. The optical variations cannot be explained on chemical grounds because the mineral shows very little chemical variation but they can be explained on the basis of Al/Si ordering. The v{021} sectors (Pa setting) are composed of optically triclinic bands, and the k{110} sector consists of both triclinic bands and monoclinic homogeneous domains. An electrostatic charge of the Al/Si ordered structure is balanced along a two-dimensional atomic arrangement exposed on the side face of a growth step. If the Si tetrahedron is produced after the calcium ion, the Si ion will be replaced during growth by an Al ion due to the local effect of the calcium ions. When a side plane of growth steps of yugawaralite is not normal to the (010) glide plane, a symmetrical equivalence of two Si sites with respect to the Ca ion will be lost at the surface, and as a consequence ordering will occur and the symmetry of crystal will be reduced. The monoclinic, homogeneous sector might be produced on the very finely kinked surface. The space group of the triclinic sector will be P1, while that of the monoclinic sector will be Pc.

In Lower Proterozoic rocks of the Olary Province of South Australia margarite occurs in conjunction with sodic muscovite, pseudomorphing chiastolitic andalusite in graphite-rich schist, and as a pseudomorphic phase in rocks consisting of coarse muscovite together with lesser amounts of chloritoid, sillimanite, staurolite, and corundum. In the latter occurrence the assemblage (muscovite-sillimanite - chloritoid ± staurolite ± corundum) replaces massive andalusite. The margarite and sodic muscovite within the pseudomorphs lack a preferred orientation which suggests that their development was associated with the waning stages of the Palaeozoic Delamerian Orogeny (cf. Glen et al., 1977) which was the last major tectonothermal event in the region.

Within the chiastolitic andalusite pseudo-morphs, equal proportions of margarite and sodic muscovite are separated from the rock matrix by a rim of coarser-grained muscovite, which has developed at the pseudomorph margins. A suggested reaction for the development of margarite is 10Al2SiO5+1.7Ca2++1.2K++Na++10H2O⇄(Ca1.6Na0.4)Al4(Si4Al4O20)(OH)3.6+(K1.2Na0.6Ca0.1)Al4(Si6Al20O20)(OH)4+6Al3++12.4OH−.

The excess aluminium and hydroxyl ions from the above reaction leave the pseudomorph system but probably react with free quartz and more K+ ions to produce the muscovite fringe. 6SiO2+2K++6Al3++12OH−⇄K2Al4(Si6Al2O20)(OH)4+8H+.

The above reactions are pertinent only for margarite and sodic muscovite produced by the pseudomorphism of chiastolitic andalusite.

Margarite and sodic muscovite in the muscovite- chloritoid - sillimanite ± staurolite ± corundum rocks replace coarser-grained (up to 1 mm) muscovite, sillimanite, corundum, and chloritoid; staurolite is unaffected. The coarse muscovite of the earlier pseudomorphic assemblage contains 7–16 mole % paragonite in solid solution whereas the sodic muscovite assocated with margarite contains 22–33 mole% paragonite in solid solution. Margarite contains negligible muscovite but substantial (17–26 mole%) paragonite in solid solution. The phases plagioclase and paragonite were not detected in any of the investigated samples. Staurolite has an Mg/(Mg+Fe) value of 0.21 and associated chloritoid a value of 0.20.

It is possible that much of the previously described sericitic alteration of andalusite (cf. D'arcy, 1977) within schists of the north-eastern Willyama Complex (north of Broken Hill) involves the production of margarite.

Rhodochrosite has been discovered as a minor component of two manganese deposits in Scotland. At Islay it occurs as coatings and veinlets on and within hollandite-pyrolusite-hematite-goethite mineralisation. Two foram microfossils were found within the carbonate which is considered to have formed from the interaction of organic-rich groundwater and seawater. The Dalroy rhodochrosite has the form of stromatactis-like cavity infill structures and veinlets in a mineralogically complex manganese-iron ore in which braunite, bustamite, manganoan ilmenite and pyrophanite have been identified. Intergrowths of rhodochrosite and native copper grains occur in a calcite matrix within the infill structures. These intergrowths are typically one micrometre across, but achieve diameters of up to 50 µm. The genesis of the Dalroy rhodochrosite is more problematical, although a hydrothermal source is most likely.

An unusual paragenesis of chromite, nickeline, cordierite, and red-brown mica occurs in veins, pods, and schlieren in serpentinized ultramafic rocks at La Gallega and Los Jarales in Máilaga province, Spain. The chromites in this paragenesis are low-ferric, ferrous-rich aluminous chromites with exceptionally high vanadium content ranging between 1·8 and 2·9 wt % V2O3 and high zinc content ranging between 0·5 and 1·0 wt % ZnO. A comparison of chromite composition with available experimental data, together with paragenetical and textural evidence, suggests that the chromite, cordierite, and red-brown mica crystallized at magmatic temperatures between approximately 1300° and 1000°C at low oxygen fugacities and maximum pressures below 10 kb, probably near 5 kb.

Klajite, MnCu4(AsO4)2(AsO3OH)2(H2O)10, the Mn-Cu-bearing member of the lindackerite group, was found in Jáchymov, Czech Republic, as the second world occurrence. It is associated with ondrušite and other arsenate minerals growing on the quartz gangue with disseminated primary sulfides, namely tennantite and chalcopyrite. Electron-microprobe data showed klajite aggregates to be chemically inhomogeneous at larger scales, varying from Mn-Ca-rich to Cu-rich domains. The chemical composition of the the Mn-rich parts of aggregates can be expressed by the empirical formula (Mn0.46Ca0.22Cu0.07Mg0.02)∑0.77(Cu3.82Mg0.14Ca0.03Zn0.01)∑4.00(As1.94Si0.06)∑2.00O8[AsO2.73(OH)1.27]2(H2O)10 (mean of seven representative spots; calculated on the basis of As + Si + P = 4 a.p.f.u. (atoms per formula unit) and 10 H2O from ideal stoichiometry), showing a slight cationic deficiency at the key Me-site. According to single-crystal X-ray diffraction, klajite from Jáchymov is triclinic, P, with a = 6.4298(8), b = 7.9716(8), c = 10.707(2) Å, α = 85.737(12)°, β = 80.994(13)°, γ = 84.982(10)°, and V = 538.85(14) Å3, Z = 1. The crystal structure was refined to R1 = 0.0628 for 1034 unique observed reflections (with Iobs > 3σ(I)), confirming that klajite (Mn-Cu member) and ondrušite (Ca-Cu member) are isostructural. The current data-set allowed determination of the positions of several hydrogen atoms. Discussion on hydrogen bonding networks in the structure of klajite as well as detailed bond-valence analysis are provided.

Wakabayashilite is a rare mineral with ideal formula [(As,Sb)6S9][As4S5]. Its structure consists of an [M6S9] bundle-like unit (M = As, Sb) running along the [001] axis and [As4S5] cage-like molecules. In this study, samples of wakabayashilite from different occurrences (Khaidarkan, Kyrgyzstan; Jas Roux, France; White Caps mine, USA; Nishinomaki mine, Japan) were selected to verify the possible presence of different molecular groups replacing the As4S5 molecule. Given the chemical (electron probe microanalysis-wavelength dispersive spectroscopy), spectroscopic (micro-Raman) and structural (single-crystal X-ray diffraction) results obtained, it appears evident that only the As4S5 molecular group is present in the wakabayashilite structure and that the apparent non-stoichiometry reported in literature is actually due to unreliable chemical analyses. The structural role of the minor elements (Cu, Zn and Tl) in wakabayashilite is also discussed.