Hydrated phosphate containing hydroxyl, phosphuranylite group
Specific gravity: 5.65
Hardness: 2 to 3
Streak: Light yellow
Colour: Golden yellow to ochre yellow
Solubility: Soluble in acids
Dehydration: H2O is entirely lost by 300oC Dana Environments
Dumontite is a secondary uranium mineral
At the type locality, the Shinkolobwe mine, Kambove District, Haut-Katanga, DR Congo, dumontite is found in pockets in torbernite in the oxidised zone of a uranium deposit (Mindat, AM 10.131, HOM), associated with torbernite (Mindat, HOM).
Near Nogales, Arizona, USA, dumontite is associated with uranophane, kasolite and autunite (HOM).
At Goodsprings, Nevada, USA, dumontite is associated with kasolite (HOM).
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