Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 55. (Budapest 1963)

Kaszanitzky, F.; Rózsavölgyi, J.: Halloysite pseudomorph after calcite from Gyöngyösoroszi

8 f. kaszanitzky cfr j. rózsavölgyi The material is preponderantly halloysite, with some hydrargylhte. Assessment was made on the basis of Miheyev's book (2). On the thermic curve, there shows, after a great initial water loss (at 150), a smaller endothermic cone (at 230). and after a high endothermic cone (at The problem was raised whether the mineral could not be metahalloysite. One cannot decide the question on the basis of the diagram, since there was no basic reflexion on the graph. It is our contention, however, that the large initial water loss, observable on the L)TA curve, can derive only from halloysite. In the case of metahalloysite, the water loss is considerably smaller. Since the halloysite — metahalloysite transformation is irreversible, the material could have come into being only at a temperature below 50° C. as a result of a descendent solution. It is worthy of note that, according to the available literature, halloysite pseudomorph after laïcité was hitherto unknown. Ilefcrcnees : l, KASZANITZKY, F.: Genetic relations of ore occurrence in the Western Mátra Mountains, North Kastern Hungary (Ann. Ilist.-nat. Mus. Nat. Hung., 51, 1959, p. 5—28). —2. MI1XEEB, B. M.: PeHTreHOMeTpimecKiiii onpeaejinTejib MiiHcpajiOB (MocKöa, 1957). NKMECZ, E-: Halloysit Gyöngyösorosziból (Földtan. Közlöny, »3, 1953, p. 398—400). 1. Cauliflower-sliaped aggregate of halloysite pseudomorph. Single crystals in hypoparallel situation. 2. Electron microscopic photograph of material pulverized in distilled water. Characteristical tubulo-cylindrical habits of halloysite well discernible, x 20,000 3. 1 lectron microscopical picture of halloysite. White line within individual tubes resultng from lack of material. X31,000 4. Cylindrical and internally empty halloysite crystals. Vesicular structure of crystals visible in center of picture. X 31,000. 560), a sharp exothermic cone (at 940). This corresponds to about a 90% halloysite and 10% hydrargyllite content. Fig. 1. DTA curve of examined material. At the authors' request, G. PÁRTA Y made electron microscopic pictures of the sample. The characteristical tubulo-cylindrical habits of halloysite is well discernible on the three photographs submitted. Explication of Plate I.