Abstract
The phase equilibrium studies of the PbS–Sb2S3 join were carried out by the evacuated glass tube method and DTA at temperatures above 400°C. In addition to the end-members of stibnite and galena, three minerals, zinkenite, robinsonite and boulangerite, and five synthetic phases D, E, F, H and I were found on this join, and their chemical compositions, thermal stabilities and crystallographic properties were determined.
Stibnite melts congruently at 546°C. Zinkenite has a composition of 9Pb·11Sb2S3 and melts incongruently to robinsonite and liquid at 546°C. A eutectic reaction between stibnite and zinkenite occurs at 516°C. Robinsonite having 4PbS·3Sb2S3 composition melts incongruently to phase D and liquid at 582°C. Phase D having a composition of 5PbS·3Sb2S3 is stable on the PbS–Sb2S3 join at temperatures from 510° to 590°C, at which it melts incongruently to phase E and liquid. Phase E with an ideal composition of 7PbS·4Sb2S3 is stable at temperatures from 584° to 603°C and melts incongruently to boulangerite and liquid at 603°C. Phase F with a composition of 2PbS·Sb2S3 is stable from 490° to 584°, at which it decomposes to phase E and boulangerite. Boulangerite with a composition of 5PbS·2Sb2S3 melts incongruently to phase H and liquid at 640°C. Phase H having a composition of 3PbS·Sb2S3 is stable only at a temperature range from 625° to 647°, and incongruently melts to gelena and liquid at 647°C. Phase I has a composition of 16PbS·5Sb2S3, stable from 610° to 636°C, at which it decomposes to phase H and galena.
