The genesis of china-clays in the neighbourhood of Guiscriff is not related to the presence of the peat which is situated on top of the clay layer in the lower parts. The formation of this peat is subsequent to the formation of china-clay. This china-clay was formed under the action of fluids of deep-seated origin of which the remains are included in the quartz veins stretching along the quarry.

A technique is described whereby powder specimens of controlled volatile content may be obtained for X-ray analysis.

Single crystals of gibbsite were partially dehydrated to boehmite in a hydrothermal atmosphere. Most of the boehmite crystallites show preferred orientation that can be explained by the octahedral linkage. Further heating in air leads to a tetragonal γ-Al2O3 whose crystallites also are oriented. The orientations give information about structural details. At about 900°C a transformation γ→θ-Al2O3 takes place. In this case too the crystallites are oriented. The oxygen chains lying parallel to the a-axis of gibbsite are strongly bound and are taken over in every new lattice during transformation.

The technique of replica casting of ceramic materials and the various methods of mounting and examination are described. Co-ordination of optical properties of the peels and X-ray analysis is considered. The uses of peels in showing orientation of clays settled under gravitation and also effects of plastic deformation are discussed.

Association of minerals such as zincblende, galena, chalcopyrite, pyrite, quartz, illite and chlorite (magnesium-rich type) has been observed in ores and also in the alteration zone adjacent to ore bodies of “Kurokō” (the black ore) deposits in Japan. Recently, in some ore bodies, detailed mineralogical studies have shown that non-metallic minerals in ores and the adjacent alteration zone are those poor in magnesium, iron and potassium, such as pyrophyllite, kaolinite, diaspore, quartz, 26 Å- and 30 Å-clay minerals. The 26 Å-clay mineral is a mixed-layer mineral of illite and its hydrated form. The 30 Å-clay mineral is a regularly interstratified montmorillonite-(aluminous) chlorite clay mineral. The presence of brucite is also usually suggested. An environmental condition to form ore deposits with such a mineral association may be a leaching condition, under which ions such as magnesium, iron and potassium were liable to be partially leached away or to precipitate as hydroxides rather than to form silicates such as illite or chlorite.

Size graded fractions of ground quartz and other silica minerals are prepared by gravity settling for particles greater than 2 microns Stokes' diameter and by centrifugal methods for smaller sizes. The size distributions of the prepared fractions are determined by counting and sizing with an optical microscope or with an electron microscope. The volume-surface diameter ΣND3/ΣND2 is used both for calculating the specific surface of the fractions and for comparing the projected area diameters used in counting, with the Stokes' diameters.

An X-ray study of the chamosite occurring in the ironstone beds near Easton Neston, Northamptonshire, has shown that probably the whole of the worked ironstone at this point is part of the Main Oolitic Ironstone Group of the Northampton Sand Ironstone formation. The boundary between the Main Ironstone in this area and the Chamosite-Kaolinite beds which overlie it has hitherto not been clearly identifiable, but it is now certain that the boundary is not more than 2 ft. 6 ins. below the top of the worked ironstone.

A focusing X-ray powder camera is described in which the degree of focusing varies with 2θ and can be made a maximum for any one reflection. It is of simple design and has two main uses:—(a) for a routine identification of the main clay mineral groups by their basal reflections, and (b) for the detection of very small amounts of any one crystalline component in a mixture.

The flat-layer method of X-ray diffraction and conditions for focusing are discussed.

A vapour pressure method of glycerol treatment of clays is described and its advantages over normal methods noted.

A method of adapting a 9·0 cm X-ray camera is described