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delafossite
Delafossite is a copper iron oxide mineral with formula CuFeO2 or Cu1+Fe3+O2. It is member of the delafossite mineral group with a general formula ABO2, a group characterized by a sheet of linearly coordinated A cations stacked between edge-shared octahedral layers (BO6). Delafossite along with other minerals of the ABO2 group has been recognized for its electrical properties from insulation to metallic conduction.〔 Delafossite is usually a secondary mineral that crystallizes near oxidized copper and is rarely a primary mineral.〔
==Composition==
The chemical formula for delafossite is CuFeO2 and was determined through chemical analysis of the pure mineral by G. S. Bohart of the Chemistry Department of Stanford University. The ratio given was very close to Cu:Fe:O=1:1:2 with a slightly more iron than copper. Rogers.〔 attributed this fact to a small amount of hematite in the sample. In order to determine the composition of delafossite Rogers used the Ziervogel process. The Ziervogel process is used to test for the presence of cuprous oxides by looking for the "spangle reaction" which produces thin flakes of metallic silver when cuprous oxide is mixed with silver sulfate. When Rogers heated powdered delafossite with silver sulfate solution, the spangle reaction occurred. The only oxides possibilities to consider for delafossite are cuprous copper and ferrous iron. Rogers concluded that the iron was combining with the oxygen as a radical and that it only acted as a radical. This indicated that the copper in delafossite was in the cuprous rather than the cupric form. Hence he concluded that the composition of delafossite was probably cuprous metaferrite, CuFe3+O2. This composition was later confirmed by Pabst by the determination of interionic distances in the crystal lattice.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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