In my description of the mineral rashleighite, which was given in this magazine in 1948, I mentioned that most of the mineral from the Bunny mine, St. Austell, was in colour light blue-green, but that it was also sometimes true turquoise-blue. Likewise, at the Castle-an-Dinas wolfram mine, St. Columb Major, there occurred rarely in addition to the blue-green rashleighite a true turquoise-blue mineral which was first assumed to be turquoise and later rashleighite. It has now been found, however, that this turquoise-blue mineral is in fact true turquoise, and distinct from the green rashleighite, Specimens of this turquoise were found at the Bunny mine, associated with varlamoffite.

In a preliminary note on the dolomite contaet-skarns of the Broadford area, Skye (Tilley, 1948, a), a brief account was given of the constitution and environment of these multizoned assemblages at the contact of the Durness limestone succession with the Tertiary Beinn an Dubhaich granite.1 No detailed survey of the numerous parageneses was then attempted, and it is the purpose of the present paper to fill this gap and to discuss the genetic problems of these skarn assemblages.

Evidence for the existence of four series of alkali-felspars has been obtained from X-ray studies of over forty analysed felspars.1 Optical studies confirm these findings, but suggest that transitional forms may occur. The four series are: high-sanidine- high-albite; sanidine high-albite; orthoclase low-albite;microcline-low-albite. Highsanidinc has the optic axial plane parallel to (010) in the potash-rich members, whereas it is perpendicular to (010) in sanidine.

The D'Arcy Exploration Company's boring, put down in 1938-39 near Aislaby, Eskdale, passed through three Permian evaporite beds. A petrological account of the rocks of the lower evaporite bed has been given in an earlier communication (Stewart, 1949). The present paper deals with the petrography of the middle evaporite bed.

It has long been known that if a diamond is heated in pure oxygen, or even in air, to a temperature of about 700° C. or higher (depending on the initial quality of the diamond), it will be wholly or partially oxidized to CO or CO2, but that if the diamond is heated in the absence of oxygen—preferably in vacuo—to a temperature of about 1500° C. or higher (again depending on the initial quality of the diamond), it will be wholly or partially converted to graphite. For complete conversion the graphite is always poly crystalline. The partial conversion of diamond to graphite is, however, of considerable interest, because when graphite forms on a single crystal of diamond it exhibits a strong preferred orientation.

In 1937 G. Nagelschmidt described a new silicophosphate mineral obtained from basic slag. It resembled the earlier described silicocarnotite (A. Carnot and A. Richard, 1883; D. P. Riley and E. R. Segnit, 1949) in its solubility in citric acid. Nagelschmidt gave optical, chemical, and X-ray data which indicated that the material had a composition of approximately 7CaO.P2O5.2SiO2, and agreed closely with a phase reported by G. Trömel (1943) in his investigation of the system CaO-P2O5-SiO2. The material was further considered by M. A. Bredig (1941), who published cell dimensions worked out from powder photographs, assuming that nagelschmidtite was a solid solution of tricalcium phosphate in a predicted high-temperature hexagonal form of dicalcium silicate. R. L. Barrett and W. J. McCaughey (1942) gave further data, chiefly connected with phase relationships in the binary system Ca2SiO4-Ca3P2O8. Finally, S. O. Agrell (1946) published further data on the slag mineral, giving the chemical analyses and optical properties of two samples, together with a discussion of the phase relationships of the material in slags, and hence in the binary system mentioned above. The name 'nagelschmidtite' is due to Barrett and McCaughey.

Leonard James Spencer, Keeper of Minerals in the British Museum (Natural History) from December 1927 to July 1935, joined the Department of Mineralogy officially on January 1, 1894, filling a vacancy caused by the death in 1892 of Thomas Davies. Davies had served in the Department since 1857. Trained by Nevil Story- Maskelyne, Keeper from 1857 to 1880, he had taken a great share in the arrangement and labelling of the mineral collection and in his later years had also had charge of the collection of rocks. Spencer was almost equally well qualified as a petrologist and as a mineralogist. He had studied chemistry at the Dublin Royal College of Science before going to Cambridge, where he studied geology as well as mineralogy and chemistry and gained the Harkness Scholarship for Geology in 1893. The examination for the vacancy at the Museum was held in August 1893 and Spencer was the successful candidate.

In the explanation of sheet 65 of the Geological Survey of Scotland an outcrop of aegirine-granulites was described from Glen Lui, 1¼ miles SSE. of Derry Lodge. Brief descriptions of some of the rocks were given and it was suggested that they might be metamorphosed igneous rocks having distinct affinities with the borolanites of Assynt. Such a correlation, it was felt, would be of importance in assessing the age of metamorphism in the Central Highlands. Harker (1932) made the further suggestion that these rocks might originally have been a tuff which had subsequently become metamorphosed.

White mineral coating joint-faces in quarries in the Northampton ironstone (Inferior Oolite) was long ago recorded as allophane. W. D. Herman who determined the mineral from the surface of a sandstone rock in a quarry opened in 1871 also analysed an unnamed white earthy mineral from crevices in the ironstone and obtained a composition close to that of fully hydrated halloysite.

During the six-inch geological survey of that ironstone field in 1939–44 the occurrence of similarly situated white incrustations and joint infillings was found to be widespread especially in the shallow workings where the ferrous minerals chamosite and chalybite have been oxidizedto produce a limonitie ore.

The investigation which has led to this description of a new mineral began because of a suggestion by Dr. W. F. Foshag, when on a Visit in 1951 to the Mineral Gallery of the British Museum (Natural History), that a brown cut gemstone exhibited as olivine had perhaps been incorrectly determined. More recently, Dr. Foshag has stated that the idea came from Dr. George Switzer, who as a result of an X-ray powder photograph taken in June 1950 of a similar specimen in the collection of the United States National Museum in Washington concluded that his material was not olivine and was likely to be a new species. The present work would not have been pursued had it been realized at the time that Dr. Switzer intended to continue the study when he had suitable material for analysis.

Early in 1947 a black, opaque, radioactive mineral resembling samarskite in appearance was discovered at Mavnzi in the Tete distrier of Mozambique, Portuguese East Africa. Two small specimens, one a rough twinned crystal with trigonal symmetry (fig. 3), were sent by h. M. Macgregor; then Director of the Geological Survey of Southern Rhodesia, to the British Museum (Natural History) for investigation, and a chemical analysis by E. Golding (table I, no. 2) followed later in the same year. X-ray photographs of fragments and powder from both specimens were taken, but revealed on development no diffraction spots, lines, or haloes. Only after prolonged heat-treatment could powder lines characteristic of crystalline material be obtained. The metamict nature of the mineral before heat-treatment is not unexpected in view of its chemical composition, optical isotropy, and glassy fracture.

Three statistical tests, depending upon the probability distribution of X-ray intensities, have been applied to orthoclase, sanidine, and albite. It is concluded that these three felspars posses centres of symmetry, justifying the assumption of holohedral symmetry made in earlier structure analyses.

Baron Karl Ludwig von Reichenbaeh (1788-1869) was born at Stuttgart, ennobled in 1839 by the King of Wiirttemberg, and died at Leipzig. But he spent most of his life in Austria, where he had iron works and estates in Moravia and Galicia and a castle near Vienna. Earning a livelihood as a copyist in the state archives, he was able to obtain a university education, and he started his career as a works chemist. He produced many papers on the distillation products of coal, tar, oil, &c, and was the discoverer of creosote and solid paraffin. He gained considerable notoriety with his ideas and books on what he called 'od' or 'odylic force', a combination of animal magnetism, light, heat, force of crystallization, &c., capable of producing hypnotism. The fall in 1833 of a shower of meteorites, which he witnessed near his works at Blansko in Moravia, fired his intense enthusiasm for the subject of meteorites, on which he wrote 29 scientific papers (1835—65) and many newspaper articles.

The confirmation of the presence of potassium salts in the Permian evaporites beneath the Whitby district, first found in the D'Arey Exploration Co.'s Eskdale no. 2 (Aislaby) boring (G. M. Lees and A. H. Taitt, 1945), and the discovery by Imperial Chemical Industries in their Eskdale no. 3 (Sleights), no. 4 (Sneaton), and no. 6 (Upgang) borings that these salts exist in workable quality and quantity, has been recorded in a recent historic paper by Dr. A. Fleck (1950). The successful outcome of this boring campaign may well lead to the outstanding development of the present century in economic mineralogy in Britain.

For the cutting of chips from rocks preparatory to thin-slicing, it has been standard practice for many years to use notched soft iron disks, manually armed with diamond powder. The latest machines employing cutting-disks of this type at the Geological Museum were built at the Government Training Centre, Ascot Works, Letchworth, to the design of the late Dr. H. H. Thomas and of Mr. W. Ward of the Centre. These are powered with 0.25 horse-power variable speed direct current motors, giving a maximum disk speed of 280 revolutions per minute. By means of rheostats, control of speed as sensitive as that obtainable with a treadle type of machine (see A. V. Weatherhead) is achieved. The normal speed for cutting is 160 to 180 r.p.m. In cutting a hard rock such as chert, it may be necessary to recharge the disk with diamond several times during the operation. The rock-specimen is held in a steel clamp with hardwood liners, mounted on a swinging arm. The rock is held in contact with the disk by the tension of a spring, or, during delicate work, by the pressure of the hand.