Samples of agate and quartz incrustations from different parent volcanic rocks of certain world-wide localities were investigated by EPR, CL and trace element analysis. In all agate samples the following paramagnetic centres were detected:, E′1, [AlO4]0 [FeO4/M+]0 and [GeO4/M+]0. Centres of the type [TiO4/Li+]0 and [TiO4/H+]0, which were detected in quartz of the parent volcanics, are absent in agate. Generally, the abundance of centres (silicon vacancy) and E′1 centres (oxygen vacancy) in agate is remarkably higher than in quartz. The high defect density in agates points to rapid growth of silica from a strongly supersaturated solution probably with a noncrystalline precursor.

CL microscopy reveals internal structures and zoning in agates and quartz incrustations which clearly differ from those discernible by conventional polarizing microscopy. The CL spectra of agates differ from those of quartz from crystalline rocks. At least three broad emission bands were detected in the CL spectra: a blue band of low intensity, a yellow band at about 580 nm, and an intense red band at 650 nm. The CL emission at 650 nm shows some relations to the hydroxyl or alkali content and the abundance of centres and E′1 centres. The emission intensity increases during electron bombardement due to the conversion of different precursors (e.g. ≡Si-O-H, ≡Si-O-Na groups) into hole centres. Another conspicuous feature in the CL spectra of agates is the existence of a yellow emission band centred at around 580 nm. The predominance of the yellow CL emission band and the high concentration of E′1 centres are typical for agates of acidic volcanics and are indicative of a close relationship between the two.

Cathodoluminescence (CL) imaging and spectroscopy, as well as backscattered electron imaging, were used to assign the occurrence of several mineral phases and rock structures in altered nordmarkites and calcite-bearing granites from the Nb-Zr-REE deposits from Khaldzan Buregte and Tsakhir (Mongolian Altai) to three events: (1) intrusion of barren nordmarkites; (2) intrusion of small bodies of calcite-bearing granites with metasomatic alteration of the wall-rocks; and (3) alteration by F-rich fluids.

Unusual red and yellow CL caused by Fe3+ and Mn2+ emission centres were detected in microcline and albite. Fe3+ centres were also established (along with others) in quartz, zircon, and possibly in fluorite.

Magmatic and metasomatic rock structures and internal structures of the minerals coexist in the samples. The primary magmatic features were in part preserved during alteration. In contrast, the internal and the centre structures may be changed during alteration even in non-replaced mineral phases. Euhedral minerals may be formed by secondary processes as shown for lath-shaped albite. The occurrence of pseudomorphs, the inheritance of elements during replacement, and the mechanical effects of secondary minerals on earlier mineral phases during metasomatic growth are proposed as criteria for the reconstruction of the mineral succession in altered rocks. Snowball structures may be formed as a result of metasomatic alteration rather than as a magmatic intergrowth.

Cathodoluminescence (CL) microscopy and spectroscopy combined with SHRIMP ion probe measurements were carried out on detrital zircons from the Cretaceous Weferlingen quartz sand (Germany) to distinguish and characterize different zircon populations.

Investigations by CL microscopy, SEM-CL and BSE imaging show that there are three main types of zircons (general grain sizes of 100–200 µm): (1) apparently weakly zoned, rounded grains with relict cores, (2) well rounded fragments of optically more or less homogeneous zircon grains showing CL zoning predominantly parallel to the z-axis, and (3) idiomorphic to slightly rounded zircon grains typically showing oscillatory euhedral CL zoning. A fourth type of low abundance is characterized by well-rounded grain fragments with an irregular internal structure showing bright yellow CL.

High-resolution CL spectroscopic analyses reveal that blue CL is mainly caused by an intrinsic emission band centered near 430 nm. Dy3+ is the dominant activator element in all zircons, whereas Sm3+, Tb3+, Nd3+ have minor importance. Yellow CL (emission band between 500 and 700 nm) is probably caused by electron defects localized on the [SiO4] groups (e.g. related to oxygen vacancies) or activation by Yb2+ generated by radiation. Variations of the integral SEM-CL intensity are mainly controlled by the intensity of the broad bands and the Dy3+ peaks.

SHRIMP analysis provides in situ high-resolution U-Pb dating of single zircon grains and confirms different ages for the evaluated different zircon types. The measurements show that the U-Pb ages of the zircons from Weferlingen scatter over a wide range (340 to 1750 Ma), backing up earlier conclusions that the quartz sand from Weferlingen is quite heterogeneous in terms of provenance.

The cathodoluminescence (CL) characteristics of plagioclase phenocrysts in water-quenched lavas from the 1983 eruption of Etna have been investigated to examine the application of plagioclase CL to the study of magmatic processes. The phenocrysts have a green luminescent inner zone that is sharply bounded by a blue luminescent outer zone, with the boundary often coinciding with a concentric zone of glass inclusions.

Strong compositional differences between the green (An70–An75) and blue (An50–An60) luminescent areas are interpreted as the result of two phases of growth under differing conditions. The green luminescent cores are considered to be anorthite-rich cumulate crystals from a basic magma which have been disrupted by the injection of a more evolved melt, resulting in heterogeneous nucleation and crystallization of the outer blue luminescent zone. The relationship between the CL and the trace element contents of the plagioclase crystals is discussed.

Natural and synthetic scheelite are investigated by time-resolved laser-induced luminescence to detect and ascribe various luminescence lines to a variety of REE. The selectivity of detection is possible by using different time delays after excitation, different gate widths and different excitation wavenumbers and allowed to detect REE in samples where they are hidden by intrinsic luminescence and not visible in the steady-state spectra as well as by cathodoluminescenee. Luminescence of Pr3+, Er3+ and Tm3+ are detected even with low concentrations and in the presence of Tb3+, Dy3+ and Sm3+. Luminescence of Ho3+ and Yb3+ is firstly detected in natural scheelites and luminescence of Eu2+ and Ce3+ is preliminary suggested.

Cathodoluminescence (CL) provides a sensitive analytical probe of the near-surface region of insulating materials, and some new examples of the strengths of the technique are presented using recent data from the University of Sussex. Analysis of float glass shows that by spectral and lifetime resolved data it is possible to separate the emission bands from excitonic, intrinsic imperfections, and impurities in various valence states, as a function of their depth beneath the surface. Correlation of the CL data with those from Mössbauer, ion beam and other analyses then provides the basis for models of the defect sites. CL from a second glass, ZBLAN, reveals the presence of microcrystallites and growth defects, and the work underpins confidence in the high purity gas levitation method of ZBLAN production. New results on CL of wavelength shifts with crystal field of Mn in carbonates are presented, and of Nd emission from Nd:YAG. The effects are directly linked to surface damage and dislocations caused by sample preparation steps of cutting and polishing. Methods to minimise the damage, by furnace or pulsed laser annealing, and chemical routes, are mentioned. Such surface preparation damage has a profound effect on all CL monitoring, whether for fundamental studies or mineralogical applications. Finally, a route to eliminate such problems is demonstrated, with consequent improvements in luminescence, transmission and laser performance of surface waveguides. The implications of improved surface quality range widely from mineralogical CL imaging through improved photonic materials and epitaxial growth to elimination of surface damage, and additional information.

Detailed electron-microprobe line profiles and small-area compositional maps of zoned garnets in a sample of high-pressure-high-temperature granulite show features inconsistent with commonly applied diffusion models. Larger grains of an early garnet generation have their highest Ca contents in domains away from the rim or inclusions but show a sharp fall in Ca balanced by increased Mg and Fe (and slightly higher XMg) towards inclusions and the rim. In domains with secondary biotite, the sharp decrease in Ca is accompanied by variations in XMg dependent upon proximity to biotite, thus producing one-sided, asymmetric profiles with XMg lower against biotite. As a consequence, rim compositions of the same grain are different on the sides adjacent and away from biotite and there is no relationship between grain size and rim XMg. Such a zoning pattern requires that grain-boundary diffusion is as slow as volume diffusion and implies the absence of a diffusion-enhancing grain-boundary fluid phase during the majority of the rock's high-temperature exhumation history. Diffusion models ignoring this probability could yield either cooling rates that were too fast, or extrapolated ages based on closure temperature models that were too old.

A second garnet generation in the same rock, grown in a Ca-rich domain resulting from kyanite breakdown, has irregularly distributed patches, identified by compositional mapping, containing higher Ca than the first-formed garnet but at lower XMg. Use of such garnet compositions for geothermobarometrical determination of the high-pressure granulite stage would clearly lead to erroneous results. The presence of such contrasting garnet compositions in a granulite-facies rock is clearly evidence of disequilibrium, and further supports the proposition that there was a lack of an effective transport medium even at the mm scale.

Uraninite is widespread as an accessory mineral in the Erzgebirge granites. It occurs throughout the entire comagmatic series of strongly peraluminous S-type Li-mica granites and has been discovered in more evolved transitional I-S type biotite and two-mica granites, but is rare in those of A-type affinity. Textural relationships and chemical ages imply that uraninite is of magmatic origin. Its composition is variable with a proportion of U plus radiogenic Pb between 71 and 99 mol.%. Uraninite has incorporated Th, Y, and the REE in total amounts between 1 and 29 mol.%. Elements such as P, Si, Al, Ca, and Fe are subordinate. Uraninite from two-mica and Li-mica granites is low in ThO2 (0.8–6.5 wt.%), Y2O3 (0–0.8 wt.%) and REE2O3 (0.1–0.6 wt.%). In contrast, biotite granites from the Kirchberg pluton contain uraninite which is enriched in these components (in wt.%) (ThO2 = 5.6–11.0, Y2O3 = 0.6–5.5, Ce2O3 = 0.1–0.6, Dy2O3 = 0.2–1.1). Commonly, the lanthanide and actinide contents in uraninite correlate poorly with those in the host granite. In S-type Li-mica granites as well as fractionated two-mica and biotite granites, uraninite is the dominant contributor to the bulk-rock U content. Here the proportion of U approaches 80–90%.

Goldmanite, the vanadium analogue of grossular and andradite, was found as subrounded green porphyroblasts ranging from 0.1 to 1.7 mm in size in the carbonaceous black slates from the Deokpyeong area of the Ogcheon belt in Korea. A radiating aggregate of slightly curved blades of goldmanite crystals displays birefringence and replaces the fine-grained black matrix. The V2O3 content ranges from 21.9 to 26.6 wt.% (24.0 wt.% average), higher than previously reported values. The calculated mole % of the goldmanite end-member ranges from 72 to 91. Its cell dimension was calculated to be 12.04 Å from X-ray diffraction. The black slate in the Deokpyeong area is the richest known accessible source of relatively pure goldmanite.

Two Mg-Al spinels (FAS1 and FAS2) in high-grade hornfels from the Toal de Mason skarn (Predazzo Monzoni, NE Italy) were investigated by means of single crystal X-ray diffraction and electron microprobe analysis in order to evaluate the last intra-crystalline closure temperature.

The evidence provided by crystal chemical data from the investigated spinels, compared with that for two other spinels from a websterite dyke and a chlorite schist (TS2 and SP78a, respectively) with similar chemical characteristics, yielded a new empirical geothermometer. This allowed estimation of intra-crystalline temperatures as low as c. 400°C and indicates that the closure temperature of FAS1 and FAS2 is c. 500°C i.e. 150–200°C lower than the spinel crystallisation temperature.

Detailed analysis of the crystal structures of minerals and inorganic compounds containing oxocentred [OCu4] tetrahedra reveals the following principle for relationships between oxocentred tetrahedra and tetrahedral oxyanions (Tn+O4)−(8−n) with T = S6+ or V5+, or triangular pyramidal oxyanions (SeO3)2− (which may be considered as (SeO3E)2− tetrahedra assuming the lone pair E of selenium to be a fourth ligand): (Tn+O4)−(8−n) tetrahedra are ‘attached’ to the oxocentred tetrahedra so that their grounds (O-O-O and Cu-Cu-Cu) are parallel to each other and the mutual orientation is regular (O corners are exactly under Cu corners). We propose to describe these relationships as ‘face-to-face’, meaning that the oxocentred and cation-centred tetrahedra ‘meet’ along their ‘whole’ triangular faces. Geometric characteristics of ‘face-to-face’ relationships are discussed.

End-members and species defined with permissible ranges of composition are presented for the true micas, the brittle micas, and the interlayer-deficient micas. The determination of the crystallochemical formula for different available chemical data is outlined, and a system of modifiers and suffixes is given to allow the expression of unusual chemical substitutions or polytypic stacking arrangements. Tables of mica synonyms, varieties, ill-defined materials, and a list of names formerly or erroneously used for micas are presented. The Mica Subcommittee was appointed by the Commission on New Minerals and Mineral Names of the International Mineralogical Association. The definitions and recommendations presented were approved by the Commission.