No abstract

No abstract

No abstract

Abstract. Pentlandite has a wide compositional range in the Fe-Ni-Co-S system and the Fe-Ni-S system. The metal : sulfur atomic ratio is approximately 9 : 8. The Co content of pentlandite from the Kamaislii ore deposit and one from the Outokumpu ore deposit (Knop et al. 1965) varies from a Co-free to nearly a Co9S8 composition. Pentlandite forms a complete solid solution between (Fe, Ni)9_+xS 8 and Co9+_xS8 in the 600°-300 °C temperature range. On the other hand, it is presumed that the pentlandite solid solution decomposes into two fields toward the (Fe, Ni)9S 8 and Co9S8 members at 200 °C. The field of solid solution at 500°C is the most extensive and includes all of the other solid-solution fields. The metal : sulfur ratio of the solid solution varies systematically, i.e., the Fe-rich field sinks toward the Fe-Ni-Co plane away from the M9S 8 section, and contrarily the Ni-rich field shifts toward the sulfur apex. The d044 value decreases with increasing S, Ni, or Co contents in pentlandite. The Kainaishi pentlandites, Iwate Prefecture, Japan, lie within or close to the solidsolution field at 300 °C, showing a very good correlation with the Co : Ni ratio of the homogeneous natural pyrrhotite phase.

The conditions of formation of malayaite, CaSnOSiO4, were studied via hydrothermal synthesis, and the region of the solid solution between malayaite and sphene determined. It was found that the immiscible region exists at temperatures lower than 615°± 15 °C. The peak of the solvus was experimentally determined to be Ca(Sn*hTi~h)OSiO4. X-ray powder diffraction patterns of the solid solution showed a successive change from malayaite to sphene with the change of composition. The relation between the d(200) and d (002) values and the tin content of the solid solution was found to be linear. The occurrence is reported of malayaite from pyrometasomatic ore deposits in south-western Japan. It is concluded that malayaite would have been formed in the front of skarn, in the quartz or calcite veinlets cutting skarn, and in the altered zones of tin-bearing minerals.