The copper-bearing horizon of the Udokan deposit is composed of gray fine-grained quartzitelike sandstones. The principal nonmetallic minerals are quartz and feldspar. The ore complex is of bornite, chalcocite magnetite, pyrite, and chalcopyrite.The sulfide mineralization is nonuniformly distributed; together with fine disperse disseminations there are very rich sections, amounting in places to almost continuous sulfide ores. The textures of the ores are disseminated, with lens-shaped flecks, less often massive; the oxide ores are brecciated and filmy or crusty.The ores in this deposit are characterized by two main mineral parageneses, spatially separated and containing two varieties --magnetite--bornite-chalcocice and pyrite-chalcopyrite. Sulfide, mixed, and oxide types of ore are distinguished by their degree of oxidation. For working these, flotation enrichment with collective concentrate production is recommended. The quality of the concentrate from the chalcopyrite ores is less good than that of the chalcocite-bornite ones, and moreover, as the copper oxide content of the ore increases, the process of separating it gets more difficult.Analysis of the information on the distribution of components in ore varieties, obtained during surveying of the deposit, gave the following results:i) The magnetite-bornite-chalcocite ores are richer in copper; as the copper content of the ore increases, the magnetite content increases but the zircon content decreases.ii) The silver and bismuth contents of the ore increase with the bornite content.ill) The silver and gold are mainly associated with the chalcocite.iv) The h~n-tite andbarren sandstones have enhanced silver contents. v) Electromagnetic separation causes bornite to go into the magnetic fraction and chalcocite into the nonmagnetic fraction.The relations between the elements are important, and also their spatial concentration. In the deposit we can distinguish three sections containing ores of different qualities. 35Magnetite--bornite-~halcocite ores predominate in section I. In this section the relative copper oxide content is lower but its absolute content is higher.In section III we find the highest silver content; it is found that, in comparison with sections I and If, the silver content of the ore increases with the copper content.~e complex relations between the elements require us to estimate the commercial value of the extracted ore, and on the basis of the results to select the first section for working. However, in order to perform these calculations, we must devise a technology for processing the ore to give high concentration of the elements in the intermediate products and concentrates with sufficiently high extraction.Institute of Mining, Siberian Branch, Academy of Sciences of the USSR (IGD SO AN SSSR), Novosibirsk. Translated from Fizlko-Tekhnlcheskie Problemy Razrabotk/ Poleznykh Iskopaemykh, No. 2,

The thermal decomposition of monomineral pyrite was studied in an inert atmostphere. From an analysis of the values of the thermal effects, an interpretation of the hree physicochemical processes recorded in the thermoanalytical curves is proposed.Both Paulik [1 ] and Berg [2] stated that three endothermic effects are observed in the thermoanalytical curves of pyrite: at 450-480 ~ 530-570 ~ and 630-690 ~ successively increasing in height. The endothermic effect at 630-690 ~ is interpreted as the thermal dissociation of pyrite and the destruction of its crystal lattice. The transformations at 450-480 ~ and 530-570 ~ however, are, interpreted differently by different researchers. Some authors [3] assume that the effect at 530-570 ~ has no connection with the dissociation of pyrite, while data of other authors [4] indicate that pyrite partially dissociates, yielding pyrrhotine. According to Berg and co-workers [2] the endothermic effect at 450-480 ~ is caused by evolved impurities and gaseous or liquid inclusions, and also by defects in the crystal lattice. The thermal process at 530-570 ~ is attributed by these authors to the evolution of oxidized "non-equivalent" sulfur located on the surface of the pyrite. Simultaneously they observed an increase in magnetic susceptibility, due to the appearance of pyrrhotine.In the present paper thermoanalytical results obtained with monomineral natural pyrite and analysis of the values of the thermal effects are reported. ExperimentalThe initial specimen was obtained by selection under a binocular microscope and contained (in mass per cent) 46% iron, 52% sulfur and 2% quartz. The thermoanalytical curves were obtained using a Hungarian MOM derivatograph, at a heating rate of 10~ in a stream of dried and purified helium. To purify the helium, it was passed through sulfuric acid, melted calcium chloride (to remove moisture), and subsequently pyrogallol and copper chips heated to 500 ~ (to remove oxygen). The inert gas was introduced into the upper part of the thermoblock of the derivatograph (above the crucibles holding the sample and the reference 4

No abstract