Morphotypes of the quartz basic rhombohedra and crystallization conditions

Resumo

An analysis of the combinatorial–morphological types of faceting for a quartz crystal head has provided 23 types of combinations of faces of basic positive and negative quartz rhombohedra, among which three full-face morphotypes are generally observed under natural conditions. The theoretical occurrence rates are obtained for these morphotypes under isotropic growth conditions, and a morphological analysis is performed over seven samples of natural quartz crystals. A method is proposed for estimating some most important parameters of the crystal formation system: the ratio of variation in the central distances to the faces of crystal rhombohedra, which is related to its growth rates; the ratios of the intermediate growth rates of the rhombohedra and prism, the index of infection with Dauphiné twins, and the feed dissymmetry factor.