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Notes on mineral growth from the archive of V.I. Stepanov (UBSS Proceedings v.21(1))

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Stepanov,V.I., 1998. Notes on mineral growth from the archive of V.I. Stepanov. UBSS Proceedings, 21(1) , pp 25-42 Download PDF.

Abstract: This paper comprises three separate texts, compiled from the unpublished archive of the late V.I. Stepanov. The texts all discuss the examination of both structure and texture during the study of mineral aggregates. The first text demonstrates how the Curie Universal Principle of Symmetry can be used in the study of mineral aggregate structures and textures. By this means some mineralogical problems were solved, for example: so-called "collomorphic" aggregates of lussasite and chalcedony crystallise from real solutions, not gels. During this study, it was found that the structure of an aggregate is determined by the position of the growth centres of individuals and by the kinetics of the crystallisation process, not by the phase state of the crystallisation medium. A study of metasomatic substitution by todorokite in marine volcanic tuffs confirmed this. It was also found that different structures may form during synchronous crystallisation of a homogeneous aggregate. Application of the Curie Principle to the whole crystallisation space revealed a new and more exact definition of texture. The second text examines the factors affecting the morphology of cave mineral aggregates. These are: crystallisation kinetics, method of transfer of the feeding solution, and mass-transfer symmetry in the medium of crystallisation. The typical forms of subaerial aggregates and ensembles are described. Some paragenetic ensembles have such distortions of structure, texture and morphology that they are best described as hybrid textures; names for these textures are suggested. A new term "kora" is proposed for an association of aggregates generated by the same crystallisation environment in all the space of synchronous crystallisation. The third text proposes that the term "typomorphism" should be returned to its original meaning: occasional and individual features in the morphology of minerals. An example is given of the very varied and individual corallite textures that grow in the subaerial conditions of karst caves.

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