The Differential Thermal Analysis of Ore Minerals (II) : On Minerals of the System Cu-Fe-S

鉱石鉱物の示差熱分析(II) : Cu-Fe-S系鉱物について

The Differential Thermal Analysis of Ore Minerals (II) : On Minerals of the System Cu-Fe-S

Creators Sugaki Asahiko

Creators Shima Hiromi

Creators Kitakaze Arashi

Differential thermal analysis (DTA) was performed on natural and synthetic minerals of the system Cu-Fe-S to detect their thermal behavior such as phase change. It was carried out by method analizing in nitrogen atmosphere or by method using a sealed vacuum silica tube as sample holder. Calcined aluminum oxide was employed as an inert material. The rate of ascending temperature was regularly 5℃/min. during the analysis. The DTA curves (Fig.3) of pyrite show a large endothermic reaction beginning at 690℃ or 722℃ at which phase change from pyrite to pyrrhotite occurs. The curves (Fig.4) of natural pyrrhotite present two endothermic peaks which correspond to γ-type magnetic anomaly and β-type magnetic transformation at 240℃ and 320℃ respectively. The β transformation of monoclinic pyrrhotite requires more large amount of the latent heat than that of hexagonal pyrrhotite. The DTA curves (Fig.8) of covellite by both methods of the evacuated silica tube and nitrogen atmosphere show a strong endothermic reaction beginning at 508℃ and 475℃ respectively. It seems to indicate formation of digenite by dissociation of covellite. The curves (Fig.9) of chalcocite also show large and small endothermic peaks beginning at temperature from 100℃ to 105℃ and at temperature from 400℃ to 460℃, corresponding to two transitions from orthorhombic to hexagonal form and from hexagonal to cubic form respectively. The curves (Fig.10) of chalcopyrite have a distinct endothermic peak which seems to represent the latent heat of transformation from α-form of tetragonal lattice to γ-form of cubic face centered lattice, beginning at 554℃ (evacuated silica tube) or 540℃ (nitrogen atmosphere). The curves (Fig.11) of bornite indicate an endothermic reaction with two steps at approximate 200℃ and 270℃. It is considered to represent the high-low inversion of bornite polymorphism. Cubanite is also found to transform from low temperature form to high temperature form by the DTA curves (Fig.12) showing a distinct endothermic peak beginning at 254°±3℃. In the case of the reaction accompanied with dissociation of sulfur, the reaction temperature obtained by both methods differs. Namely such an endothermic reaction in the nitrogen atmosphere occurs at lower temperature than that of the means using the evacuated silica tube method.

[ISSN]0372-7661

[NCID]AN00244228