The minerals to be described in this paper were collected, in conjunction with W. E. Fraser, who was carrying out a detailed study of the borolanite, from the road-metal quarry, opened in 1938, at Allt a' Mhuillin, Loch Borolan, Assynt, Scotland. They occur in pegmatitic patches and veins in borolanite.

This mineral is one of the chief constituents of the pegmatites. It forms large cleavable masses, associated with orthoclase, melanite, and a little dark mica. Calcite, sphene, zircon, and orthite are present as accessories. It often fills interstices between crystals of orthoclase. A preliminary examination has indicated that it is a common constituent of the spots in some types of borolanite, and further work will have to be done to determine its importance in this connexion. This is the first definite record of the occurrence of cancrinite in Britain.

The deposits of sulphur at Krisuvik, Iceland, have long been known. They were described geologically in detail by Vincent who also discussed their probable origin, but gave no chemical analyses other than rough determinations of the percentages of sulphur and matrix in various samples. From the flame spectrum Vincent thought that thallium might be present.

Apart from popular descriptions by travellers and casual references in guide-books, little attention appears to have been given in literature to these deposits in more recent years. Sporadic attempts at working the sulphur economically were made by the Danish Government during the eighteenth century and later by a Danish merchant round 1832. These were abandoned, however, owing to cost of transport. There is little likelihood of their renewal in the immediate future unless the deposits are found to contain some other element(s) of sufficient market value.

The olivines, which are the subject of this note, were obtained from a series of basaltic lavas and dikes on Ubekendt island, which lies off the west coast of Greenland in latitude 71 ° N., longitude 54 ° W.

The optical properties of the olivines were investigated in order to determine any range in composition; such variations might have been expected in the very thick lava series. From this aspect, however, the results are disappointing, the composition range being small. However, it is thought that the results may have a certain interest in showing the relative accuracy obtainable in the measurement of refractive indices and optic axial angles. The usual determinative methods have been slightly varied. It is the purpose of this note to describe these variations and to compare the relative speed and scope of the method used with those obtained by other methods.

Waldemar Lindgren described in 1924 a mineral present in nickel ores from southern Nevada which in colour, hardness, and stability differs from polydymite from Grüneau mine at Sehutzbach, between Betzdorf and Daaden in Rhenish Prussia, and yet matches so-called ferriferous polydymite from Vermilion mine, Sudbury, Ontario. He proposed the name violarite both for the mineral from Nevada and for the ‘polydymite’ from Ontario on account of the violet-grey colour of the mineral on polished sections. Lindgren assumed that the iron found in the first analysis of ‘polydymite’ from Ontario was due to admixture with pentlandite and thence deduced nickel disulphide as the possible composition of violarite. In the light of subsequent results it is relevant to mention that Lindgren and Davy's work was based upon the study of polished ore sections but not in polarized light.