The North Qôroq syenite centre forms part of the Gardar Province of South Greenland. Extensive metasomatism, associated with the evolution of syenitic magmas, has resulted in redistribution of the rare-earth elements (REE), originally concentrated by magmatic processes, in both the syenites and surrounding granite-gneiss and quartzite country rocks. An important host for REE is apatite which can occur in significant quantities. Metasomatic apatites show complex, concentric, but irregular patterns of zonation, clearly seen using CL and BSE imaging. This zonation is related to successive pulses of metasomatising fluids. Electron microprobe analysis confirms the presence of significant quantities of REE in the apatites. The dominant cation exchange mechanism proposed is Ca2+ + P5+ ⇌ REE3+ + Si4+. In contrast to apatites from the nearby Ilímaussaq intrusion, there is no significant Na present in the structure and exchange reactions involving Na+ and REE3+ for Ca2+ have not occurred.

Apatites from the quartzite are fluor-apatites, while those from the granite-gneiss are more Cl-rich. These differences reflect the fact that granite-gneiss apatites are original and modified by metasomatism, whereas, those in the quartzite are metasomatic in origin. REE were probably transported as carbonate, fluoride or fluor-carbonate complexes, and reflect the activity of a F−-rich, CO2−3-rich fluid phase.

The 100 Ma complex LCT-type composite pegmatite- aplite dykes, intruded into various units of the Southern California Batholith, are known to contain bismuth minerals. Jahns and Wright (1951) reported the following primary and secondary bismuth minerals from the quartz-rich cores of a number of dykes in the Pala district, San Diego Co., California: native bismuth, bismuthinite, bismite, bismutite, and beyerite.

The instrumentation and procedure is described for the extraction of very small and pure samples from polished mounts and thin sections of minerals, for X-ray analysis and other micro-analytical techniques. It uses a stand-mounted, tunable ultrasonic probe (400 W/15–50 kHz) inclined at 45°C to a microscope stage. The tip of the probe, usually a steel needle, is located on the desired mineral and an appropriate ultrasonic frequency is selected. Very fine powders are produced from grains as small as 0.01–0.005 mm. A distinct advantage of this technique is that, as different minerals powder at different rates and different frequencies, it is possible to separate a single mineral from an intergrowth of two or more minerals.

Spontaneous fission reactions occurred in several uranium deposits in SE Gabon approximately two billion years ago. The reactor zones, between 10 to 50 cm thick, are found in Proterozoic sandstones and consist of high-grade uranium ore mantled by illite and/or chlorite (Gauthier-Lafaye et al., 1989). During a mineralogical study of sandstones (quartz arenites) underlying a natural fission reactor at Bangombé (20 km south of the Oklo uranium deposit), we have found several grains of a uranous silicate, coffinite, with unusually high concentrations of phosphorous and enriched in light rare earth elements (LREE).

Guidelines on mineral nomenclature published by the Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association (Nickel and Mandarino, 1988) include the following statement: "If an artificial substance has been given a name, and a mineral corresponding to that substance is subsequently discovered, the name given to the artificial substance does not necessarily have to be applied to the mineral".

The geochemistry of late Caledonian minettes from across the orogenic belt is compared in order to constrain the composition of the Caledonian sub-continental lithospheric mantle (SCLM). All the minettes are similar petrographically and chemically and several samples have characteristics typical of near primary mantle melts. Samples from the Northern Highlands and the Caledonian foreland show enrichment in many trace elements (notably LILE and LREE) relative to those from the Grampians, the Southern Uplands and northern England, coupled with distinct Nd and Sr isotope characteristics. Processes such as fractional crystallization, crustal assimilation, and partial melting played a negligible role in creating the differences between the two groups which reflect long-term, time-integrated differences in the compositions of their SCLM sources. The Great Glen Fault appears to represent the boundary between these two lithospheric mantle domains. Other currently exposed Caledonian tectonic dislocations cannot be correlated directly with compositional changes within the SCLM. The chemical provinciality displayed by the minettes shows some resemblance to that within other late Caledonian igneous suites, including the newer granites, suggesting that the minettes may represent the lithospheric mantle contributions to these rocks.

Ojuelaite was described from its occurrence at the Ojuela mine in Mapimi, Mexico by Cesbron et al. (1981). Those authors suggested that the phase was isostructural with whitmoreite (Moore et al., 1974), a phase of interest because of the unique arrangement of Fe octaheda in its octahedral sheet.