A minor phase in iron-ore sinters has been synthesized and identified as a clinopyroxene with the approximate formula Ca1·0(Ca0·14Al0·60Si1·08)O6. This composition shows that it consists largely of the hypothetical Tschermak's molecule, M2+SiO6. The small size and sparse distribution of this phase in most iron-ore sinters has previously hindered analysis.

Early in the year 1918 Mr. Atehur Russell picked up at the old antimony-lead mine at Glendilming in Eskdale, Dumfriesshire, Ipecimens of the antimony-lead ore Jound there, in which were small cavities lined with a drusy layer of mimlte crystals; these, being markedly deeper in eolour than the stibnite forming part of some of the specimens, belonged to a different species, and probably a sulphantimonite of lead. Mr. Russell blought some of the specimens to the Museum, and some of the small crystals were examined with the view of determining the species to which they belong.

It is but seldom, at least in the experience of the writer, that a new mineral locality is now found in this country. By a mineral locality I mean, not a spot where one or two specimens may be gathered, but one at which there is a supply sufficient to entitle it to be recorded as a spot likely to be productive to a sequence of gleaners; and such as holds out hopes of its yielding specimens of more than average excellence.

Sitathali is an olivine-bronzite chondrite, consisting largely of olivine (Fa18) and orthopyroxene (Fs19) with minor amounts of a clinopyroxene (Ca36Fe12Mg52), plagioclase (An12), nickel-iron, troilite, chromite, and a phosphate (apatite or merrillite). The chemical analysis of a 4 gm sample gave SiO2 39·85, TiO2 0·10, Al2O3 2·84, Cr2O3 0·35, FeO 13·27, MnO 0·28, MgO 23·01, CaO 1·84, Na2O 0·65, K2O 0·15, H2O+ 0·23, H2O− 0·05, P2O5 0·25, FeS 5·09, Fe 10·22, Ni 1·58, Co tr. total 99·76. The metal displays Neumann bands, some deformed, as well as areas of apparent flowage. Troilite locally exhibits twin lamellae and in places replaces kamacite in the plessite fields. Elsewhere it is in braided veinlets and globules, both reflecting former melting. The varied textures suggest a complex post-formational history encompassing several deformational events presumably due to breakups and possible extraterrestrial impacts.

The distribution of potassium and strontium, potassium and barium between feldspars and aqueous chloride solutions was studied at 700°C, 2 kbar and 800°C, 2 kbar respectively. The distribution of Sr and Ba between coexisting feldspar and chloride solutions is not ideal; Sr and Ba are enriched in feldspar relative to solution. In order to estimate the phase state of the chloride solutions, special experiments were conducted using the synthetic fluid-inclusion method in the systems KCl-BaCl2-H2O and KCl-SrCl2-H2O at 700–800°C, 2 kbar. It was shown that (0.5M KCl+0.5M SrCl2) aqueous solution is homogeneous at 800°C, 2 kbar. The 0.25–0.5M SrCl2 solutions are homogeneous at 700°C 2, kbar. The (0.5M KCl+0.5M BaCl2) solution is homogeneous at 700°C, 2 kbar and heterogeneous at 800°C, 2 kbar. Margules parameters for describing the excess energy of mixing of the (K,Sr)- and (K,Ba)-feldspar solid solutions were calculated. The integrated values of excess energy of mixing () were estimated for the different binary feldspar solid solutions, and a correlation of with the crystallochemical parameter ρ = (RA-RB)/D(Me-O) was observed. Feldspar solid solutions can be subdivided into three groups based on the relationship between , p and the stability of the solid solution.

Troilite is a sulfide that occurs commonly in meteorites. In the laboratory, it can be synthesized by gas-solid reaction of metallic Fe and H2S-H2 gas mixtures. In this research, the arc-discharge method was used to synthesize troilite. The resulting spherules are up to 2–3 mm in diameter and composed of troilite, pyrrhotite and metallic Fe. Nanometer-sized hollow carbon fibres and balls occur on the surface of the spherules. The features and coexisting relationships of the constituents of the spherules were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the phenomenon of transformation of pyrite (FeS2) into pyrrhotite (Fe1-xS), troilite (FeS) and metallic Fe under arc-discharge reducing conditions were examined.

The Indian peninsula, though considered to be a very stable part the earth's crust and hence called the 'Indian Shield', shows in different parts evidence of formerly having sustained epicontinental basins, in which sedimentation occurred. These sediments are now found in detached prisms as crystalline gneisses and schists in different parts of India, e.g. in the Madras Presidency, Bihar and Orissa, Central Provinces, Central India, and Rajputana. They have been found overlying the ancient gneigses (Archaean), and belong to a division known in Indian geology as the Dharwar System.

Lengenbachite is one of the interesting minerals which occur in the dolomite of the Binnenthal, and we owe our knowledge of it, as of many other new species, to the careful investigations conducted in recent years by Mr. R. H. Solly at that remarkable locality. The crystallographic and physical characters, so far as they have proved capable of determination, have been already described by Mr. Solly in the pages of this Magazine (vol. xiv, p. 78). The material which he kindly placed in my hands for chemical examination consisted of cleavage-plates, exhibiting brilliant metallic lustre, and of foliated aggregates of thin greyish-black crystals. Some of the crystals were partially covered with a thin, white incrustation readily removed by boiling dilute hydrochloric acid, a reagent which appeared to be without action on the lengenbachite.

Many minerals of the rhomhie system are of markedly columnar habit, with the axis of elongation, or vertical axis, as one of the biseetrices of the angles between the optic axes. Such a crystal, in a section parallel to the vertical axis, gives straight extinction. It is natural to expect, and is perhaps generally assumed, that a section slightly oblique to the vertical axis will give nearly straight extinction. The object of the present note is to inquire how far this is true, and in what possible cases a serious error may arise.

The accurate determination of α:[001] and 2V in members of the aegirine-augite series often presents difficulties owing to strong absorption and dispersion, especially as high angles of tilt on the universal stage are often involved. Both of these angles depend on the location of α, and this operation is the one most subject to error.

An alternative procedure is the determination of A:[001], the angle between an optic axis and [001]. This angle is very easily and accurately determined and varies systematically with composition. It can be derived from the values for α:[001] and 2V, while conversely values of α:[001] and 2V can be obtained from A:[001] by reference to standard curves.

The discovery of tin-ore in Ankole (south-western Uganda) led to a great deal of prospecting on the part of qualified and unqualified, experienced and inexperienced, individuals, not only in the vicinity of the original discoveries, but also in many other parts of the Protectorate. One of the results of this activity was the finding, by a prospector, of a deposit of alleged coal at a spot rather less than 25 miles WNW. (approx.) of Kampala and about 35 miles NW. of Entebbe. With reference to this, the discoverer was told by the Geological Survey that his hoped-for fuel was in reality tourmaline, but inasmuch as it was associated with a pinkish-buff mica characteristic of the stanniferous pegmatites of Ankole, further search might disclose the presence of tinstone.

In the basaltic lavas of Iceland certain porphyritic crystals of unusually large dimensions, occur embedded in the matrix of the rock, and from an early date have received the notice of writers on the geology of that island. Amongst these authors might be mentioned :—Professor Forchhammer, Dr. F.A. Genth, M. A. Damour, Prof. Zirkel, M. P. Schirlitz, and M. R. Bréon.