Baldanza, Bartolo and Triscari, M. (1978) Iconografia cristallolisica di ematite del basamento sedimentario etneo. Accademia Peloritana dei Pericolanti, Classe di Scienze FF. MM. NN., LVI. pp. 239-257.
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The basal faces of large platy hematite crystals from the sedimentary basement of Etna exhibit plenty of well known crystal growth patterns: short regular tongue-like terraces, different kinds of spirals, more or less poligonized, triangular structures. Previous step heights measurements of some of these patterns were made by precision multiple beam interference, whilst high precision phase contrast microscopy helped to determine the sequence of crystal growth patterns and led to argue about environmental evolution, whose late stage was characterized by a stern undersaturation. This last yelded plain explanation of the final short but intense dissolution suffered by hematite, whose basal faces were lastly etched and a new type of etch figure appeared: they consist of long wavy tongues, composed by innumerable steps of extreme fineness, that permitted more precise step heights measurements: 2.30 - 6.83 - 13.68 - 20.55 - 27.50 - 34.74 - 41.30 - 48.10 amstrong (higher values were note performed). All measured values are integral multiples of the smallest value 2.30 A. This, in turn, is the same order of magnitude of hematite.
Hence the fundamental model followed by hematite dissolution process is explained and it is quite reasonable to expect that also the growth process of hematite is, at least in part, governed by spirals of a step height of 2.3 amstrong.
|Subjects:||M.U.S. - Miscellanea > Atti Accademia Peloritana > Classe di Scienze Fisiche, Matematiche e Naturali > 1978|
M.U.S. - Miscellanea > Atti Accademia Peloritana > Classe di Scienze Giuridiche, Economiche e Politiche > 1978
|Depositing User:||Dr A F|
|Date Deposited:||06 Nov 2012 12:31|
|Last Modified:||24 Jan 2013 09:38|
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