For the first of the three minerals to be described in the following pages we are indebted to Mr. W. G. Fearnsides, who collected it in North Wales in the autumn of 1908, and we desire to express our best thanks to him for the readiness with which he placed at our disposal enough suitable material for a complete analysis. The other two minerals were collected by ourselves.

A specimen in the British Museum, consisting mainly of brown chalybite and decomposed iron pyrites--the latter mostly converted into earthy oxides--bears upon its surfitce and in its cavities a number of thin prisms encrusted with a botryoidal yellowish substance which covers a great part of the decomposed specimen. On close inspection the needles are seen to be Cronstedtite, mostly but not entirely converted into black limonite, and the encrusting substance consists mainly of phosphate (with a little carbonate) of lime. The latter is sometimes crystalline on its surface.

The natural glasses, found as small corroded pieces scattered on the earth's surface and in alluvial deposits in a few limited areas, have long presented a puzzling problem; and many theories have been propounded to explain their origin. They have been known in southern Bohemia and western Moravia since before 1787; and similar material has since been found in the Dutch East Indies, Malay States, Australia, Tasmania, French Indo-China, south China, Philippine Islands, and quite recently in the Ivory Coast in West Africa [M.A. 6-106]. These glasses are distinct in chemical composition from volcanic glass (obsidian), and there are no volcanoes in the districts where they are found. They have been given the names m oldavites, billitonites, austral ites, Darwin glass, indoch inites, rizalitcs [M.A. 4-422; 6-403], &c.

Despite a wide range in parent rock compositions, from analcime-olivine theralite to analcime-tinguaite, clinopyroxene phenocrysts in the Square Top intrusion show limited compositional variation. The crystallization trend of the pyroxenes (principally sahlites) lies approximately parallel to the diopside-hedenbergite join of the pyroxene quadrilateral, and in addition reveals slight enrichment in acmite. The limited iron enrichment in the pyroxenes (and in olivine phenocrysts in the theralites and tinguaites) stemmed from progressively more hydrous liquid fractions whose ferric/ferrous iron ratios increased during differentiation.

If the visitor standing at Wherry Town on the south-western end of the esplanade at Penzance looks seaward he will observe at low tide at some distance from the shore a low scaweed-clothed rocky shoal (fig. 1), and from his now very conventional surroundings it is difficult to realize that upon this shoal, always surrounded by water, there existed many years ago a rich tin mine, unique in the boldness of its conception, romantic in the extreme in its situation and execution, and withal the effort of a poor working miner.

Very fortunately in the year 1790, during the hey-day of its career, this remarkable mine was examined by a very competent observer in the person of John Hawkins (1761 ?-1841), F.R.S., of Trewithen, Cornwall, and Bignor Park, Sussex, and it is to him that we owe most of the details concerning its mode of working, &c. The Wherry mine and its history have always fascinated me, as they must have many others, and in re-telling the old story I have endeavoured to collect all the known facts, both as to the mine itself, its mode of working, and its mineral productions, and in so doing pay tribute to its gallant and resourceful originator Thomas Curtis.

The parish of Engie in Banffshire lies on the south shore of the Moray Firth, to the East of the Spey. From the Spey to Buckle on the East the rock is Old lied Sandstone, which extends from the sea inland for about two or two and a half miles. This sandstone area is bounded on the south by a series of clay-slates and mica-schists. Both on the low and high grounds of this little parish, specimens of Kyanite were often picked up, sometimes associated with quartz, and sometimes with the schistose rocks of the district.

Bauxite is of twofold interest due firstly to its economic importance, and secondly to the scope it affords for scientific investigation. When these two reasons are taken into consideration, one can easily account for the enormous and rapid accumulation of literature concerning this subject. Any attempt to give a detailed account of the literature will only mean unnecessary repetition of what has been already dealt with at great length by several writers, of whom Anderson and Fox may be specially mentioned. The relation between bauxite and laterite is so intimate that a detailed study of the one is impossible without any reference to the other, and as such the description of and frequent reference to the latter should not be considered as any digression from the subject.

The orientation of the ‘rhombic section’, the composition-plane of the pericline twin, in the plagioclase felspars as an index of the chemical composition of the felspar waJ first utilized by G. yore Rath, who measured the gngle a on the face (010) between the trace of the composition-plane and the edge [010,001]. Duparc and Reinhard, in their comprehensive work on the determination of the plagioclases, quote two series of values for this angle, one due to Wiilfmg and the other to Becke. They comment on the discordance between the two series, most marked at the acid end, and add that they did not then possess suitable material for critical determinations on their own account. Wülfing's values are given in the form of a curve based on data assembled by Schmidt, and those of Becke were first given in a paper on the felspars in crystalline schists.

During the X-ray study of a new phosphate mineral, not yet published, the usual comparison was made with cell-side measuremerits of related minerals. One of these is ‘eggonite’, a rare hydrous aluminium phosphate said to occur on silver ores at Felsőbánya, Hungary. Rotation photographs of ‘eggonite’ are different from those of the new mineral, but yielded dimensions close to those of sterrettite, a new mineral from Fairfield, Utah, described last year by Larsen and Montgomery. These authors generously presented a specimen of sterrettite to the British Museum, and rotation photographs taken in the Mineral Department not only give cell-dimensions close to those published but also identical with those of ‘eggonite’. A brief account of this identification is now given not only to justify abandoning the mineral name ‘eggonite’, but also to place on record a European occurrence of a rare mineral so far described from only one American locality.

Gismondine is recorded from the Tertiary basalts of the North Atlantic region, from a total of some 40 localities in Antrim and Iceland. It occupies a well-marked position in the sequence of zeolite zones in the lavas, and the characteristic associates are chabazite, thomsonite, and phillipsite. Five new chemical analyses of gismondine from these localities show a negligible content of potash, and indicate plagioclase-type substitution, giving a series ranging from near Ca8Al16Si16O64.34H2O to near Na2·5Ca5·5Al13·5Si18·5O64.34H2O. Substitution of NaSi for CaAl leads to a decrease in refringence, birefringence, and density.

There are certain foreign minerals upon which the South African diamond has crystallized readily. The chief of these are garnet, ilmeuite, olivine, and iron-pyrites. In addition, zircon and mica are also probable inclusions. Cognate inclusions are graphite, bert of every kind, and diamond itself of unconformable orientation.

The Cambridge Museum recently acquired a number of albite specimens from Alp Rischuna, near Yals Platz in Switzerland. Many of the crystals had good faces, so that measurement of the angles seemed likely to give trustworthy crystal-elements.

In recent years there has been little essential change in the design of the petrological microscope. F. E. Wright directed attention to the improvement that could be obtained by using a full-sized condenser with a large polarizer, but the high cost of the latter seems to have restricted its use to a few special models.

With the introduction of ‘polaroid’, a thin, intensely pleochroic film mounted between glass disks, this restriction no longer holds. A polarizer can be supplied of sufficient size to cover an ordinary Abbe condenser, while the analyser no longer requires the compensating lenses which usually accompany a calcite prism, with the indirect result that the definition of the interference-figure is improved.

The Benue trough is a graben structure containing folded Upper Cretaceous sediments. Mid-Tertiary to Recent rift-valley type vulcanicity in and near the trough was mainly basaltic (in the north at least), salic lavas being now represented mainly by a few eroded plugs. The Nigerian rocks are regarded as a practically extinct sub-province within a larger Gulf of Guinea alkaline province, dominated by the voluminous and still active vulcanicity of the Cameroun rift. The two structures have the same trend as other graben features further south along Africa's western margin.

Large sodic plagioclase crystals in a basalt plug within the Nigerian sub-province have rounded edges and more calcic overgrowths. They probably crystallized at deep crustal levels but are unaccompanied by any of the mafic phases that normally crystallize from basalts under high pressure. However, spinel crystals and olivine nodules found in a nearby plug indicate that the complementary mafic assemblage may be found not far away. Sparse published data on phenocrysts and inclusions in the Jos Plateau lavas offer some support for this suggestion.

Crystallization of sodic feldspars in basalt may have a bearing on the independent genesis of salic liquids, while apatite and magnetite inclusions in them suggest a possible link with carbonatites.

The mineral hero described was recently collected by the officers of the Geological Survey during their work for the six-inch map of the Island of Mull. It is present as minute phenocrysts in a dark, glassy, magnetite-bearing rock/which is intruded as sheets in the Tertiary lavas nearly one mile south-south-west of Pennygael.

The small rounded crystals of augite are seldom more than ½ mm. in diameter and are traversed by irregular cracks. They contain a few negative crystals, and are occasionally darkened, probably with included magnetite. They appear to have been reabsorbed to some extent by the matrix.