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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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