Zrosty bliźniacze gipsów z Koronowa

Zofia Skrzat

Abstract


TWINNING OF GYPSUMS FROM KORONOWO

Among gypsum crystals originating from Koronowo, over a dozen specimens of twins were found to be formed on [001], and developed as so-called "Karlsbad" twins, thus interpenetrant ones. The twins were divided into three groups. To the first group the specimens were assigned, on which simultaneously two types of twinning appeared, to with juxtaposition and interpenetrant twins; to the second group - interpenetrant twins, in which the twinning extends over the entire length of an individual; to the third group - those in which the twinning occurs-over a part of the length. In the last-mentioned group there were two specimens" where twins occurred in shape of a wedge. It is assumed that formation of twins of the last group is brought about, inter alia, by lattice stresses caused, in turn, by ingrowths, which -in the specimens examined here - were gypsum crystals having divergent orientation. Moreover, it ,should he said that upon the formation of the twins described above, in all probability, influenced here decisively super-saturation of solution and presence of alien ions.

The twinning was established by X-ray method, in some instances also-optically. The system of characteristic spots being obtained in the Laue's patterns. from thick slides of gypsum twins was explained, too.


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