Platinum-Group Minerals from a Hydrothermal Environment*

Three types of platinum-group minerals occurring in a low-temperature hydrothermal copper deposit near Messina, Republic of South Africa, are described. Electron-micro-probe analyses of the minerals show Type I to be an unnamed mineral approximating (Pd, Pt)a(Te, Bi)a; Type II is kotulskite, Pd(Te, Bi) that is unusually poor in bismuth, and Type III consists of compositional varieties of another unnamed mineral having a composition of (Pt, Pd)a_xT%. The minerals occur in chalcocite and clausthalite (PbSe) and are associated with bornite, quartz, epidote, and chlorite. Optical and physical properties of the platinum-group minerals are given, but no X-ray data could be obtained, owing to the small size of the grains