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.

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.

In October 1945 Count Taaffe, a brilliant if unorthodox Dublin gemmologist, in the course of examining a motley collection of gemstones, came across a small mauve stone which puzzled him greatly. The stone had the appearance, and most of thc characters, of spinel, but afforded clear evidence of double refraction. As recounted below, this stone was later found to belong to an entirely new mineral species-—the only case hitherto known where a mineral has been first encountered as a faceted gem.

The origin of the zeolites and associated minerals in vesicles in lavas is a subject on which there is considerable difference of opinion. In general there are two main views: that they are due to the action of percolating surface waters upon thc original minerals of the rock; or are associated with some stage of the cooling processes, as an after-effect of volcanism.

The occurrence of a member of the glaucophane group of minerals in Anglesey has been known since 1888, in which year Blake reported the presence of a blue amphibole in a schist exposed in the neighbourhood of the Anglesey Column, west of the Menai Bridge. In the course of his paper Blake made general remarks on the petrography of the schist and on its field relations. He dwelt at some length on the question of the identity of the blue amphibole which is its most notable constituent, describing its columnar habit and pleochroism, and recording an extinction angle of 15° with the axis of elongation (c). By comparison with a description of glaucophane due to Rosenbusch, Blake concluded that the blue amphibole from the Anglesey rock is a normal glaucophane, although it, an extinction angle as recorded by him is considerably in excess of the 4° to 6° mentioned by Rosenbusch.

During a departmental excursion to South Devon in April 1951, material was collected from the Meldon aplite quarry near Okehampton, to the north-west of the Dartmoor granite, which on examination has proved to contain the mineral columbite. The mineral is present only in very small amounts and as extremely minute crystals; nevertheless its presence is of considerable interest in that this appears to constitute the first authenticated record of the occurrence of a mineral of the columbite-tantalite series in Britain.