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 Middle Lias of Rutland, east Leicestershire, and north-west Northamptonshire was described by Judd in 1875 as comprisingan upper ferruginous member—-the Marlstone Rock Bed-—and a lowerargillaceous division of blue clays, often micaceous or sandy, and carryingbands of 'septaria' and of 'ironstone balls'. In the septaria he recordedthe occurrence of 'specular-iron, zinc-blende and pyrites'.

During the six-inch survey of one-inch New Series sheets 157 (Stam-ford) and 171 (Kettering) together with the adjacent parts of sheets 156(Leicester) and 170 (Market Harborough) a considerable area of thelower argillaceous division was mapped.

Some years ago the author gave a short description of a quartz-bearing syenite and its xenoliths occurring on the eastern side of Barnavave. The locality was revisited recently and more material wascollected, while another outcrop of syenite was discovered farther tothe north at locality 5.

The new material collected at the original locality is not very differentfrom that previously described. The syenite occurs as veins in lime-stone and, whereas all the previously described material was quartz-bearing, some of the syenite in very narrow veins is virtually free fromquartz. Again, certain specimens carry a fair amount of late-crystallizing wollastonite which may be replaced to a varying degree by pecto-lite.

In the course of a study of the corrosion products formed by seawater sprayed at a temperature of 85° F. on brass and copper sheets, a pale green compound was isolated which proved on chemical analysis to have the composition Cu2(OH)3Cl. The X-ray powder diffraction pattern of the substance was found on visual comparison to differ from that of atacamite, which has the same chemical composition. The atacamite pattern was obtained from a specimen of the mineral from Moonta, on the u peninsula, South Australia, that had been authenticated by both morphological measurement and optical study; identical patterns were obtained from a number of other specimens labelled atacamite. The pattern of the corrosion product proved to be identical, however, with that of two specimens in the Harvard collection labelled paratacamite. These were labelled as from Remolinos, Vallinar, Chile (no. 97523), and from Sierra Gorda, Chile (no. 82883).

In the course of a petrological examination of some hundreds of specimens from the Tertiary coastal dike swarm of east Greenland, collected at various times by L. R. Wager and W. A. Deer, it was decided to investigate the nature of the residual glassy mesostasis of one of the olivine-tholeiites, in the hope that it might shed some light on the trend of differentiation of the magma responsible for the bulk of the rocks in the swarm. An account of the petrology of the swarm as a whole will be published in due course, but it was thought that a note on the chemical and physical properties of this glassy residuum might be worthy of independent publication, particularly as it provides an interesting comparison with the results of work carried out by Walker (1930, 1935) on the residual glass from one of the Upper Carboniferous tholeiites from central Scotland. The general features of the east Greenland coastal dike swarm have already been described by Wager and Deer (1938) and Wager (1947).

During the Manchester University's 1946 geological excursion to Anglesey, a visit was made to Parys Mountain. At this locality small quantities of an attractive light blue mineral were found capping pyrite veins and in clefts in the rock. Larger finds were obtained in an artificial cavern which extended for fifty or sixty feet into the south-east side of the excavated pit. A specimen weighing 2½ pounds and consisting of silicified shale veneered with the pale blue mineral was collected by the author and examined in the geological research laboratory at Manchester University during the session 1948–1949. The blue mineral was identified as pisanite, and this is the first record of pisanite as a British mineral.

Parys Mountain is situated in the north-west of Anglesey close to Amlwch. Copper and to a smaller extent lead were mined throughout a period exceeding one hundred and fifty years, but operations have completely ceased since the first world war. The geological structure of the district need only be briefly outlined for the purpose of this study.

In any monoclinic crystal, the zone–axis [uvw] is perpendicular to the plane (hkl) if u/(hc2–lac cos β) = v/(kc2a2sin2β) = w/(la2–hac cos β). In particular, the normal to the face (100) is quasi–parallel to the zoneaxis [r01̄] if c/(a cosβ) approximates to a rational number r.

Epidote has a:b:c = 1•5807:1:1•8057,β 115° 24', and is often twinned on a(100). G. Friedel describes and explains these twins in terms of a pseudo–normal zone–axis [301], with an obliquity of 3° and a twinindex 3. But the choice of a pseudo–normal zone–axis is necessarily arbitrary, since it is always possible to find a rational zone–axis making an angle with any given face–normal less than any assigned angle δ: though the indices of such an axis may involve large numbers.

This paper deals with a series of soil-clay minerals which have a widespread distribution in the north-east of Scotland. The original member is a biotite-like mica which breaks down readily in the soil into (i) a vermiculite or (ii) a montmorillonite, depending on the soil-forming conditions operating. Apart from this 'clay biotite' and its decomposition products, the main crystalline constituents of the Scottish soil-clays are a member of the kaolinite group and illite (' clay muscovite'). Iron and aluminium oxides are present in all the clays in the amorphous condition, but crystalline varieties are scarce. The distribution of the minerals and their relationship to the various soft-forming factors will form the subject of a separate communication; here, the nature of the clay minerals and their interrelationships are considered.

In the course of the routine X-ray examination of a number of lowgrade iron ores in order to determine their constitution, it was observed that the calcite phase had varying interplanar spacings. Since these variations could have been due to differing solid-solution contents of other carbonates, further consideration was given to this point. The existence of these generally small amounts of solid solution is of some technological interest.

A sample of 'specpure' calcite, supplied by Messrs. Johnson, Matthey & Co. Ltd., was used to provide accurate lattice parameters and interplanar spacings for pure calcite.