Final Crystallization Products Research Articles

Thermal decomposition of cation exchange forms of zeolite A

1. After partial dehydration of zeolites A(LiA, NaA, KA, RbA, CsA, CaA, MgA) (degree of dehydration 50–70%), there is a small compression of their cubic structures with the formation of metaphases, the volume of the cubic unit cells of which remains constant upon further dehydration, while the density decreases. 2. The greatest thermal stability, determined by the temperature interval of the process of amorphization of the metaphase, is possessed by metaphases of zeolites with rather large exchange cations (K, Rb, Cs). 3. The final products of crystallization of the amorphized phase formed as a result of thermal decomposition of the metaphase areβ-eucryptite and anorthite for LiA and CaA, respectively; a mixture of hexagonal and cubic kaliophilites for KA; aluminosilicates with the composition R2O·Al2O3·2SiO2, where R=Rb, Cs, possessing no natural analogs for RbA and CsA; and magnesium aluminate of undetermined composition for MgA.

On idaite (Cu5FeS6) in Japan

The authors have arrived at the following results upon studying the idaite-bearing ores from ten different localities in Japan. 1) Idaite have been found in several deposits in Japan. The specimens from Yakuwa Mine, Yamagata Prefecture, have been unequivocally identified by X-ray powder method. The number of sites yielding idaite in Japan is expected to increase with further study. 2) Idaite occurs in the secondary enrichment zone of copper deposit in the form of secondary decomposition product of chalcopyrite and bornite, except in two sites, where it is present as final crystallization product in copper deposits formed under low temperature and pressure. 3) Hypogene idaite is contained in small quantity in bornite, together with digenite and chalcopyrite. Supergene idaite forms lattices, lamellae and veinlets buried in chalcopyrite and bornite. In some cases, it forms films between chalcopyrite and supergene chalcocite, or replaces pyrite in company with supergene chalcocite, digenite and covellite. 4) The process of secondary enrichment and oxidation of chalcopyrite and bornite may be summarized as follows; chalcopyrite→supergene bornite hypogene bornite idaite chalcocite digenite→covellite cuprite tenorite native copper

The Role of Water in Basaltic Magma I.

The crystallization of a hydrous melt in the system K2SiO3—SiO2—H2O is studied in detail to determine what are the external factors exerting the greatest influence over the character of the final crystallization product. These are found to be (a) the nature of the stresses present in the crustal horizon at which crystallization takes place and, (b) the effective pressure of the water in the pores of the surrounding rock, a pressure which is determined by the potential rate of escape of vapour from the magma as well as by the gas pressure of the water itself. Various types of environment are considered and the products of consolidation of an ideal magma of this system compared for the various cases. The probable mode of assimilation of a xenolith composed of one of the solid phases of the system in such an ideal magma is also investigated.