The Vale das Gatas tungsten mine is situated at the contact between Hercynian granite and Cambrian-Precambrian crystalline schists a few kilometers north of the village of Sabrosa, near Vila Real, in northern Portugal. Wolframite has been the principal product of the mine although several other metals of economic interest are known to occur there. The silver content of the ores was attributed by earlier workers to the presence of tetrahedrite and schapbachite, whilst this work shows matildite, pavonite, acanthite, and argyrodite to be present, together with Ag-bearing galena. The textures and compositions of these phases are described with preliminary results of fluid inclusion studies.

Efflorescent outgrowths and compact vein-like material from brucite-rich specimens is a basic magnesium carbonate and possibly a dimorph of artinite. X-ray, infrared, chemical and thermal data reveal the material to be different from known natural basic magnesium carbonates.

Holmquistite idioblasts occur in a hornblende-titanite-quartz-plagioclase amphibolite, in contact with a lithium (spodumene) pegmatite at Greenbushes, Western Australia. Unit cell parameters, chemical data and the results of a mineralogical investigation of holmquistite and associated minerals in the amphibolite are given.

In 1884, Lorenzen proposed the formula MgAl2SiO6 for his new mineral kornerupine from Fiskenæsset and did not suspect it to contain boron. Lacroix and de Gramont (1919) reported boron in Fiskenæsset kornerupine, while Herd (1973) found none. New analyses (ion microprobe mass analyser and spectrophotometric) of kornerupine in three specimens from the type locality, including the specimens analysed by Lorenzen and Herd, indicate the presence of boron in all three, in amounts ranging from 0.50 to 1.44 wt.% B2O3, e.g. (Li0.04 Na0.01 Ca0.01) (Mg3.49 Mn0.01 Fe0.17 Ti0.01 Al5.64)Σ9.30 (Si3.67 Al1.02 B0.31)Σ5 O21 (OH0.99 F0.01) for Lorenzen's specimen. Textures and chemical compositions suggest that kornerupine crystallized in equilibrium in the following assemblages, all with anorthite (An 92–95) and phlogopite (XFe = atomic Fe/(Fe + Mg) = 0.028–0.035): (1) kornerupine (0.045)-gedrite (0.067); (2) kornerupine (0.038–0.050)-sapphirine (0.032–0.035); and (3) kornerupine (0.050)-hornblende. Fluorine contents of kornerupine range from 0.01 to 0.06%, of phlogopite, from 0.09 to 0.10%. In the first assemblage, sapphirine (0.040) and corundum are enclosed in radiating bundles of kornerupine; additionally sapphirine, corundum, and/or gedrite occur with chlorite and pinite (cordierite?) as breakdown products of kornerupine. Kornerupine may have formed by reactions such as: gedrite + sapphirine + corundum + B2O3 (in solution) + H2O = kornerupine + anorthite + Na-phlogopite under conditions of the granulite facies. Boron for kornerupine formation was most likely remobilized by hydrous fluids from metasedimentary rocks occurring along the upper contact of the Fiske⇒set gabbro-anorthosite complex with amphibolite.

The Tieschitz chondrite is a disequilibrium assemblage of silicate, metal and sulphide occurring together or separately as chondrules and clasts that generally have opaque rims (matrix) of fine-grained material. Translucent, silicate-rich matrix fills channels that occur sporadically between chondrules and clasts. An angular fragment of twinned ‘clinoenstatite’ was found to be rimmed with chromium- and manganese-rich augite and surrounded by opaque matrix. The whole is set within the largest area of translucent (white) interchondrule matrix encountered. It is suggested that reaction between crystallizing undersaturated translucent matrix, opaque matrix, and clinoenstatite probably led to the partial replacement of clinoenstatite by chromian-manganoan augite at high temperature.

The transmission electron microscope is now used in a great variety of mineralogical and petrological contexts, The development of such applications over the past thirty years is illustrated by reference mainly to studies on serpentine and amphibole minerals.

The Outokumpu region of Finland is notable for the large number of Cr-rich silicate and oxide phases associated with the massive sulphide deposits. In this paper analyses of Cr-rich phases in the epidote-clinozoisite and muscovite groups are presented. The muscovite-type phase shows a maximum 80% substitution of Cr for A1 on octahedral sites with a maximum 24.7 wt.% Cr2O3. Apparent complete solid solution between this extreme composition and the fuchsitic muscovites is indicated. The clinozoisite type phase has a maximum 15.4 wt.% Cr2O3, with a composition close to Ca2CrAl2Si3O12(OH). As with the micas, complete solid solution of Cr for Al in the clinozoisite structure is indicated.

Primary allanite crystals occurring in andesitic rocks from Poros, NE Peloponnese, Greece were studied. Although the allanite shows high REE content, its presence does not affect the whole-rock REE content of the andesite. It is suggested that the formation of allanite crystals reflects the crystallization history of the andesitic rocks where allanite occurs. These andesitic rocks are the most basic rocks in which allanite has been reported.

Orbicular dioritic-noritic rocks from an area of mixed metemorphic and igneous rocks in Swat Kohistan, northern Pakistan, have been examined petrographically and chemically in order to determine the nature and origin of the orbicular texture. Using textural and compositional sequences it has been possible to relate the apparently different orbs to one another, and obtain a sequence of orb formation. The majority of the orbs comprise a series of distinct layers (shells) surrounding a central zone (core). Plagioclase, clinopyroxene, orthopyroxene and hornblende form the bulk of the shells. The cores have been extensively recrystallized. The development of a ‘comb-layered’ texture in some orbs and in associated layered rocks is comparable to that commonly described from other occurrences. A dual igneous/metasomatic crystallization history is invoked to explain the features of the orbs in this locality, the oscillatory zoning of the orbicular structure being caused by the alteration of primary minerals, such as pyroxene to amphibole, due to fluctuations in the pH2O of the magma.

Palagonites from the Red Sea consist of two zones: an orange palagonite which is a mixture of Mg-Al double hydroxide, Al-hydroxide and an undetermined Si-K phase, and a white palagonite, similar to motukoreaite, a Mg-Al hydroxy-sulphate-carbonate. This mineral, frequent in experimental alteration of glass by seawater, is discovered for the first time in natural palagonite. Hydroxysulphates and hydroxides are the precursors of phyllosilicates, generally found in palagonites. The very young palagonites of the Red Sea are the first link between the natural and experimental observations.

Metamorphosed troctolite cumulates occur interbedded with Mg-rich metagabbros in the Monviso ophiolitic massif; they have developed chloritoid, omphacite, talc and garnet during the eclogitic stage of the Eo-alpine metamorphism. The lack of penetrative deformation in the rocks has made it possible to recognize different microstructural sites of chloritoid growth, in which the chloritoid composition may vary widely and is controlled by the specific inherited chemical domain.

The chloritoid compositions are unusually rich in Cr and Mg with large variations in Fe2+/Mg and Cr/AlVI ratio. The Cr/Al ratio in chloritoid is linked to both the Cr value of the primary minerals (i.e. Cr-rich spinels, Cr-end-members in the clinopyroxenes) and a limited redistribution of Cr during metamorphism. The Fe2+/Mg ratio, while being partly affected by bulk composition of the host rocks, also varies between different microstructural sites; the highest ratio is recorded in coronas between clinopyroxene and plagioclase, lower values occurring in coronas between plagioclase and olivine.

Arsenoflorencite-(Ce) has been found at three localities in Australia—two in South Australia, and one in Queensland. It occurs as colourless to light brown scalenohedral crystals and crystal fragments in stream sediments. Electron microprobe analysis gave Ce2O3 12.97, La2O3 8.62, Pr2O3 3.35, Nd2O3 2.40, Gd2O3 1.38, Sm2O3 0.38, SrO 1.99, Al2O3 28.75, As2O5 27.02, P2O5 4.68, SO3 1.21%; calc, H2O 9.36%; total 102.11%. The simplified formula is REAl3(AsO4)2(OH)6, with Ce as the dominant RE element. Arsenoflorencite-(Ce) is rhombohedral, has space group R3m with αhex. 7.029 and chex. 16.517 Å, and Z = 3. Strongest X-ray powder diffraction lines are: 3.513(6)(110), 2.963(10)(113), 2.201(4)(107), 1.905(5)(303) and 1.753 Å(4)(220). Density is 4.096 (meas.) and 4.091 (calc.) g/cm3. Hardness is VHN10 170. Arsenoflorencite-(Ce) is brittle, breaks with a conchoidal fracture, and has no perceptible cleavage. The mineral is colourless in transmitted light, uniaxial positive, and has ω 1.739 and ɛ 1.745 (λ = 589 nm). Arsenoflorencite-(Ce) is the arsenate analogue of florencite-(Ce), and the name was chosen to indicate this relationship.

Loveringite-davidite members of the crichtonite group were synthesized at high pressure and temperature (7.5 kbar, 1000–1050 °C) from a melt of TiO2 and rare earth element (REE) enriched basaltic andesite composition. Four sets of partition coefficients for La, Srn, Ho, Lu and Sr (analogue for Eu2+) were obtained. These show that light and heavy REE are readily accommodated, but the intermediate REE are discriminated against in the loveringite—davidite structure. This confirms the previously proposed two sites (A and M) for REE substitution in the crichtonite group. Additional experiments verified the stability of REE-rich crichtonite group minerals to 20 kbar, 1300 °C and 30 kbar, 1000 °C, and indicate that this phase may be an important accessory repository for the light and heavy REE in the upper mantle.