Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 50. (Budapest 1958)
Kaszanitzky, F.: Genetic relations of the Pátka-Kőrakáshegy ore occurrence, Velence area, North Central Hungary
formed into cerussite. This phenomenon is usually quite rare. It is generally restricted to the marginal parts of the galena body, cerussite occurring there in the form of thin veinlets creeping along the cleavage planes of galena, or in the form of smaller aggregates. In galena, the following elements have been demonstrated by spectrographic analysis : Ag, Cu, Sb, Bi (I. Kubo vie s, analyst). Tetrahedrite, exceeding chalcopyrite in quantity, but succeeding the same in the sequence of formation, occurs in forms much similar to those of chalcopyrite. It is mostly found together with chalcopyrite in the hollows of sphalerite, on the borderline of sphalerite and gangue. It frequently replaces the two predominant minerals. By their optical characteristics the varieties tennantite and tetrahedrite s. str. were demonstrated. Tetrahedrite s. str. appears to be somewhat more frequent than the other variety. As the presence of cinnabar as a secondary formation is known from the occurrence, it would be reasonable to expect the presence of schwatzite. This variety could not, however, be demonstrated. Some tetrahedrite grains exhibit oxidative effects of small intensity. The sequence tetrahedrite-covellite-azurite-malachite is observed. This phenomenon of oxidation also occurs at the deeper levels. There are two generations of pyrite to be distinguished in the occurrence. The oldest one is the first formation of the entire sequence. It occurs mainly in the interior of chalcopyrite bodies : however, it is sometimes also seen in sphalerite grains. It appears throughout in well-developed hexahedral grains. Its colour is a somewhat greyish green to yellow. It is readily distinguished from the younger generation of light yellow color. The younger generation is found in smaller spots, rags, cobweb-like structures in the fissures of the gangue or of older minerals. It never forms well-developed crystals. The younger generation is weakly anisotropic. This is supposedly due to the Sb content, occurring in the form of lattice contamination. Of chalcocite, there are likewise two modifications in the occurrence. Primary chalcocite invariably occurs in small knots on the margin of sphalerite bodies. Using oil immersion and greater magnification its grains appear to be lamellar in structure. They are of a white to bluish white colour. There is scarcely any birefringence to be observed. Anisotropy, on the other hand, is marked. The rhombic modification of Cu 2 S was most probably developed out of the hexagonal one. The upper level has yielded a secondary modification of chalcocite. In this environment it was precipitated out of descendent solutions. It is of a massive texture and of a very slightly bluish white colour with weak refringency. It occurs always in the fissures and hollows of the primary ore minerals or else it forms an oxidated rim around the same. This kind of chalcocite may be further oxidized by descendent solutions whereby covellite, azurite and malachite will be formed. More significant quantities of antimonite are found on the upper part of the occurrence around the shaft driven according to the intentions of A. Földvári. Of the workings accessible at present it occurs only around the end of the north-eastern dike-gangway, at the contact of granite and slate, in the form of aggregates of thin needles of some millimetres to 2 centimetres in length. The elongated crystals exhibiting the characteristic birefringence and anisotropy occur in bundles intergrown along the c-axis. Most of the crystals are bent in consequence of translationalong (010). The surface of the individual
