The three-dimensional computer model of the Co-Cu-CoS-Cu2S subsystem T-x-y
diagram at temperatures above 800oC is represented. It is shown that the
liquid immiscibility in the binary subsystem Cu-Cu2S is transformed within
the ternary system with Co into the wide two-phase region of two immiscible
melts, which interrupts the univariant curve of the Co and Cu2S
co-crystallization. The special features of the structure of the solidus
surface of cobalt, caused by liquid-phase immiscibility are considered.