The ophiolitic rocks appearing near Monte Chiaro, characterized by serpentine masses crossed by veins of talc, sometimes of remarkable thickness, are to be found on the right of the Taro river a few miles from Borgotaro. On examination three interstratified clay minerals were found: saponite-talc, chlorite-saponite, chlorite-vermiculite, which were studied optically, with X-ray, d.t.a. and chemical analysis.

A method for determining the peptizability of various clay minerals is described. It is of considerable use for industrial purposes.

A sample of “phenyl” montmorillonite containing 10% by weight of carbon has been examined as a sorbent for nitrogen, benzene and water. The material shows only a small loss in weight on outgassing, and there is no interlamellar sorption of nitrogen and little of either benzene or water. In its behaviour as a sorbent it thus differs notably from the natural clay, from some alkyl ammonium forms of clay, and from certain “clay esters.” The small amount of interlamellar sorbed benzene is desorbed with difficulty and is sorbed only slowly. It is concluded that nearly all the interlamellar space is filled with organic material, but it is not possible to say whether this is chemically bonded or very strongly sorbed by a physical mechanism.

After CO2 and C are allocated to carbonates and carbonaceous matter, FeO and MgO are allocated to a hypothetical “average” chlorite of composition 12(Fe, MgO). 3Al2O3. 7SiO2. 10H2O, K2O is allocated to muscovite, remaining Al2O3 to kaolinite, remaining SiO2 to quartz, calculated hydroxyls usually agree well with H2O+. Calculated mineral analyses agree well with practical assessment and thermal expansion curves. Chlorite and chlorite-illite are known to occur (X-rays) in this series of clays.

The synthesis of cobaltiferous clay minerals is described. Two methods, whereby the positioning of ions in such compounds may be adduced, are discussed. The mechanisms involved in synthesis are described.

Precision intensity measurements were made on 27 00l reflexions using Mo Kα radiation. The interpretation of these results leads to the location of the Al and Si atoms of the tetrahedral layer in two different planes.

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.

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.

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.

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.