New data on the nature, paragenesis and composition of lead antimony-bismuth sulfosol found in the gold-quartz ores of the Sredne-Golgotai deposit located in the eastern part of the Mongol-Okhotsk orogenic belt are presented. It has been found that this mineral here forms two independent mineral phases (I, II) slightly different in composition and resembles the described sakharovaite from ores of the Ustarasai deposit. The difference between I and II phases is in the lack of Cu and Fe in the composition of the phase I. According to the crystal-chemical computation of the received microroengen spectrum analyses, the phase I is close to jamesonite, and the phase II is close to tintinaite. There is a suggestion that the copperless and iron-free variety of the sulfosol can formally be considered as a separate type of mineral.
Key words: minerals, bismuth jamsonite, cobellite, homologous series, gold mineralization, Middle Golgotay deposit, Eastern Transbaikalia