The thermal decomposition of alunite and of mixtures of alunite with dickite or quartz or both has been studied, and X-ray determinations of the products at various stages of the decomposition have been made. Between 600 and 700°C the product from alunite is a mixture of anhydrous alum and amorphous alumina; between 700 and 770°C the anhydrous alum breaks down into aluminium sulphate and alkali sulphate; then in the prominent 850°C endothermic reaction three-quarters of the sulphate is lost, leaving a mixture of alkali sulphate and γ-alumina. The area of the 850 °C endothermic peak may be used as a measure of the percentage of alunite in alunitized rocks (alunite-quartz-dickite mixtures).

A study has been made of a large clinoptilolite deposit in the Lesser Caucasus (Azerbaidzhan SSR). The geological conditions have been examined and a number of samples investigated by optical, electron-microscopic, chemical, X-ray, thermal, and infra-red methods. Based on these investigations and on comparison with previous literature, mineralogical, chemical, and geochemical conclusions are drawn and conditions for clinoptilolite genesis are considered.

This paper is a report on the various features of the crystallogenesis of calcite as shown in specimens collected from iron-ore skarn deposits. Although there are several forms, each showing a variety of habit, a detailed study shows that there is a unified sequence of successive habit substitution. A structural analysis of calcite based on P.B.C. (Periodic Bond Chain) vectors is then considered.

A genetic classification of clay rocks is given in which five main types are recognized. In this classification minerals of the kaolin group formed directly from hydrothermal solutions, along with sulphides, sulphates, and pneumatogenic minerals, are separated from the same minerals formed by the hydrothermal-metasomatic action of gases and vapours on aluminosilicate rocks. Some data on the occurrence of these two types in Azerbaijan are recorded. The origin of the bentonitic clays (“gilabi”) of Azerbaljan is also discussed; the geology of the deposits indicates cycles of volcanic activity and long-range transport of volcanic ash.