Rouaite with Cuprite, Malachite

specimen number:
2282049

location:
Tenke Fungurume Mine, Lualaba, DR Congo

description:
Deep blue crystalline and crystallized rouaite on a cuprite matrix with malachite.

The Tenke Fungurume mining complex, situated in the Lualaba Province of the Democratic Republic of the Congo, is a massive copper-cobalt operation located within the Central African Copperbelt. Geologically, the deposits are sediment-hosted and stratiform, occurring within the Neoproterozoic Katanga Supergroup, specifically inside the Roan Group dolomites, siltstones, and shales. Hydrothermal mineralizing events structurally emplaced rich zones of primary copper-cobalt sulfides, which tropical weathering subsequently altered into extensive, near-surface blankets of secondary oxide minerals like malachite, chrysocolla, and heterogenite. Although early geological surveys and exploratory drilling by Union Miniere began around 1900, and a joint venture attempted initial development in the 1970s, sustained large-scale industrial open-pit operations did not officially commence until 2009 under the management of Freeport-McMoRan. Following a major corporate acquisition completed in phases between 2016 and 2019, the operation transitioned to majority ownership by China Molybdenum Company, which continues extensive open-cast extraction and mechanized processing at the site today.

Rouaite is a rare secondary copper nitrate mineral that forms as an alteration product in the oxidized zones of copper deposits. Geologically, it develops under specialized conditions where weathering copper minerals react with localized nitrate solutions, which are sometimes derived from organic sources like bat guano in arid or sheltered mine environments. The mineral crystallizes in the monoclinic system and typically occurs as thin, platy or tabular crystals, small equant grains, or as delicate crystalline crusts and aggregates coating native copper or cuprite. It features a striking color range that spans from dark emerald green and bluish green to dark blue-green, exhibiting a glassy luster and a distinct green streak when tested.

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