Conichalcite with Calcite

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The vivid, almost acid-green colour of this specimen is really eye-catching. This is Conichalcite, a rare calcium copper arsenate hydroxide species which forms a series with Duftite (where lead replaces calcium). Both species are well-known at Tsumeb mine and it is possible that both are present on this specimen, as cross-sections through the vivid green velvety microbotryoidal crusts, exposed on the edges of the specimen, show distinct colour banding when viewed under magnification. A later, partial overgrowth of cream coloured rhombic Calcite crystals adds to its attraction. Ex Kessler Collection.