Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 66. (Budapest 1974)
Örkényi-Bondor, L.: The plagioclase crystals of the andesite agglomerate from the Csattogó Hill in Börzsöny Mountains (Hungary)
prevalent in the Börzsöny and Visegrád Mts. Two of these new twin laws are puplished, others are still in manuscript. The Csattogó hill lies north-west of Verőce village, while on the east and south a limiting valey gives its natural border. The andésite lapillis and bombs macroscopically and microscopically could be divided into ten types; marking was from 21/1973 to 30/1973. The plagioclase crystals in the ten types display some common characteristics, which difered from those of the plagioclases deriving from other area of the South-Börzsöny Mts. The plagioclase crystals were chosen for investigation by the Fedorow method as their size shows the avarage distribution of the size of the feldspar phenocrysts. The size of the plagioclase phenocrysts is 0.1—6.0 mm in diameter. Mostly the inclusions consist of groundmass. In some rocks, e.g. in specimen 22/1973, there were many apatite needles as inclusions. Usually the plagioclase phenocrysts are fine zoned, the colourless zones are followed by zones with many inclusions. The feldspars of that rocks which contain fresh amphibole crystals differ from those with altered amphiboles. In some case, like in specimen 21/1973, feldspar crystallized in the place of resorbed dark silicate. It is remarkable that the plagioclase crystal of medium size, e.g. in specimen 25/1973, are not idiomorphic. The larger feldspars of specimen 28/1973 have more inclusions, than the smaller ones. Not infrequently, broken crystals are observed, the originally one piece fell into parts and they moved apart, then the interspaces are filled with groundmass. If there are plagioclase crystals with inclusions and withouth one in the same rock, the latter crystals have much less anortite. Where the amphibole crystals are fresh, Fig. 7. The number of plagioclase phenocrysts as a function of grain size.
