別子鉱床酸化帯から見出されたドラフォッス鉱

概要

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Delafossite, CuFeO2, was found from the oxidation zone of the Besshi ore deposit which is embedded in Sambagawa metamorphic rocks, and is situated at the central Shikoku, Japan. It occurs as botryoidal aggregates in small cavities and as crusts filling cracks of oxidated ore in association with the supergene minerals such as native copper, cuprite, malachite, brochantite, chrysocolla, cuproallophane, hematite and goethite. It is black with submetalic luster, opaque, and pale yellowish white color in reflected light. The unit cell parameters are a = 3.020 (5) and c = 17.17 (3) Å. Delafossite from Besshi is chemically characterized by relatively high Zn content up to 9.9 wt% as ZnO. The empirical formulae with highest and lowest Zn content are (Cu0.89Zn0.11)Σ1.00 (Fe0.88Zn0.07Al0.03Ti0.01)Σ0.99O2 and (Cu.0.91Zn0.09)Σ1.00(Fe0.95Zn0.01Al0.01)Σ0.97O2 respecrively. The general formula of delafossite can be expressed as (Cu1+1-xZn2+x)(Fe3+1-xZn2+x )O2 or (Cu1+1-xZn2+x)(Fe3+1-x[]x/3)O2. Delafossite was formed by the decomposition of chalcopyrite ore associated with a small amount of sphalerite under the supergene environments.
日本鉱物科学会の論文
2008-07-30