Shinkolobweite

shinkolobweite

uraninite

fourmarieite

rutherfordine

Images

Formula: Pb1.25[U5+(H2O)2(U6+O2)5O8(OH)2](H2O)5
Uranyl hydroxide, one of the few minerals that contain rare pentavalent uranium U5+, that is also present in wyartite, richetite and nollmotzite
Crystal System: Orthorhombic
Specific gravity: 5.853 calculated for the empirical formula, 5.850 calculated for the ideal formula
Hardness: 2
Streak: Light bronze-yellow
Colour: Dark reddish brown
Luminescence: Not fluorescent under UV
Solubility: Dissolves slowly in dilute hydrochloric acid, initially turning yellowish orange, possibly due to the oxidation of U5+
RADIOACTIVE
Environments

Sedimentary environments
Hydrothermal environments

Shinkolobweite is a relatively new mineral, approved in 2016 and to date (October 2023) reported only from the type locality.

Localities

At the type locality, the Shinkolobwe mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo, uranium deposition is known to have followed the emplacement of copper and cobalt ores, and uranium-bearing heterogenite from the region has been dated to between 620 and 850 million years ago. Shinkolobweite may be among the secondary minerals that first crystallised in the assemblage and is likely to be no younger than ∼100,000 years. It was likely formed during the initial alteration stages of uraninite when the system exhausted available O2, leading to an incomplete oxidation of uraninite, or partial reduction of U6+, these favouring the persistence of appreciable concentrations of U5+ in solution. Coatings of rutherfordine, which is found in close association with shinkolobweite, may suggest that bacterial respiration or decomposition produced locally reducing conditions that favoured formation of U5+.
Shinkolobweite occurs on a specimen of massive uraninite that is richly mineralised with other secondary uranium minerals, including fourmarierite, rutherfordine, soddyite, and sklodowskite.
Shinkolobweite occurs as deep reddish-brown prismatic and bladed crystals measuring up to 0.5 mm in length (CJMP 61.5.999–1020).

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