Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 51. (Budapest 1959)

Kaszanitzky, F.: Genetic relation of ore occurrence in the Western Mátra Mountains, North Eastern Hungary

In the deposit, three generations of pyrite may be distinguished. Pyrite I. is the first-formed ore mineral of the veins. It is also frequent in the host rock. Its hexahedral crystals of 1—2 millimetre size are situated especially on the margin of the veins, forming small veinlets or nodes of variable size. In the clay seam of the veins, developed in some instances, pyrite I is the most frequent ore mineral. It also occurs in the altered andésite debris of the veins. Excepting the Szákacsurgó and "2150" veins, it is ubiquitous. However, its quantity is of no great importance. Its digested rags are frequently encountered in the crystals of the older generation of sulphides, most frequently in chalcopyrite. The second generation of pyrite does not form continuous masses. Nevertheless, its amount is greater than that of the first pyrite generation. It generally partakes in cementing the crushed sections of the veins, in the form of veinlets of 1—2 millimetre thickness. These sometimes consist of closely juxtaposed pentagon dodecahedra. Between crossed niçois the crystals exhibit well-defined anisotropy. According to Sztrókay this anomalous optical feature is a consequence of the As and Sb content of pyrite. The second pyrite generation was formed after the formation of the main ore minerals. It occurs in shapeless aggregates of ill-defined grains around the older ore minerals or in the gangue surrounding them. It may further fill the fissures of shattered sphalerite and galena in the form of a fine zigzag pattern. It is also encountered upon the crystals of the calcite veinlets appearing in the center line of the veins. There it froms incrustations of gel structure. This generation is likewise ubiquitous, excepting the Szákacsurgó vein. Large quantities occur, however, only in the Bányabérc vein where it is, together with marcasite, the latest formation. Here it has attacked or entirely replaced a significant part of older sulphide ores. The third pyrite generation occurs in the Bükkszéi and Szákacsurgó veins, mostly as a precipitate of gel structure. In the interior of the pyrite aggregates there occur idiomorphic marcasite crystals. The second generation of pyrite is, on the contrary, invariably incrusted by marcasite. In the Szákacsurgó vein pyrite III is the predominating ore mineral, beside which there occurs marcasite only. Pyrite was formed here out of descendent solutions. Spectroscopy has shown in pyrite I As, Sb and Mn, in pyrite II Ba, As, Sb, Pb, Zn, Ag, Au, Cd, Bi, Ti and Mn, in pyrite III As, Sb, Pb, Ag, Mn and Mo (analyst, I. Kubovics). The spectrogram of pyrite III has further shown an uncertain line of thallium. Galena is one of the main ore minerals of the veins, exceeded in quantity only by sphalerite. An older and a younger generation may be distinguished. Older galena is more frequent in the thicker sections of the veins, where it forms homogeneous masses of a loose structure, falling apart on pressure along lines of cleavage. Structural etching reveals a well-developed zoning, parallel to the grain boundaries. It was already established by Sztrókay that along the borders of some galena grains inclusions of mother liquor occur, visible as parallel rows of pin-pricks in the section. These rows are diagonal as related to cleavage and parallel to octahedral faces. In one section Koch has found minute grains of gold. Old galena is, together with sphalerite, one of the eldest formations of the veins. Its quantity most have been greater originally, as it has been to a considerable degree attacked and replaced by later ore minerals and quartz. The replacement begins along the rows of mother liquor