Phase relations in the Au-Ag-Te systems and their mineralogical significance

By X-ray and microscopic techniques, equilibrium relations were determined in the presence of vapor at 290 degrees , 335 degrees , and 355 degrees C, and changes in assemblages studied from about 50 degrees to 800 degrees C. A new ternary eutectic at about 304 degrees C has the approximate composition 50 percent Au, 15 percent Ag, 35 percent Te (wt. percent). Krennerite, a single mineral entity with the approximate formula Au 4 AgTe 10 , is stable up to its incongruent melting at about 382 degrees C. Sylvanite melts incongruently at about 354 degrees C. Hessite and petzite each have three polymorphs.