Thermal Studies on the Cubanite Lamellae in Chalcopyrite from the Ômine Mine

Abstract

Under the microscope, cubanite is found in lamellae and massive crystals in chalcopyrite from the Omine mine, Iwate Prefecture. The lamellae run parallel to ?? 111 ?? of chalcopyrite, as shown in Figs. 1 and 2, and are thought to be an unmixing product from a solid solution, while the massive crystals are believed to be a primary product from the ore solution. When both cubanite in chalcopyrite are heated in sealed tubes, the following process is observed. 1) No change is observed at temperatures from 300°C to 340°C. 2) At 350°C for 90 hours, at 400°C for 50 hours or at 450°C for from 5 to 10 hours, lamellar cubanite changes by mutual reactions with surrounding chalcopyrite into saw-toothed bodies, as shown in Fig. 3A. 3) At 400°C for 100 hours or at 500°C for from 5 to 15 hours, the cubanite lamellae suffer conspicuous diffusion from chalcopyrite, and thus converting into micrographic or lattice-shaped intergrowth of two minerals, as shown in Figs. 3B, 5 and 6. 4) A margin of massive cubanite changes by heating at 400°C for from 50 to 100 hours into irregular form the same as 2), as shown in Fig. 7. 5) At temperatures from 450°C to 500°C, pyrite appears in cubanite and chalcopyrite as granular, worm-like and dendritic crystals, as shown in Fig. 8 From the results of experiment, it is concluded that the solid solutionn of lamellar cubanite and surrounding chalcopyrite may be perfectly formed by heating at temperature of about 350°C in such long times as the geological process.