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Formula: (UO2)2(CO3)(OH)2.4H2O
Carbonate, uranyl mineral
Crystal System: Monoclinic
Specific gravity: 4.1 to 4.55 measured, 4.54 calculated for the empirical formula and 4.50
calculated for the idealised formula
Hardness: 2 to 3
Streak: Pale yellow
Colour: Canary yellow
Luminescence: Does not fluoresce under 360 nm light
Solubility: Soluble with effervescence in dilute hydrochloric acid
Strongly RADIOACTIVE
Environments
Localities
At the type locality, the Jomac Mine, White Canyon Mining District, San Juan County, Utah, USA,
oswaldpeetersite occurs in conglomerate that is rich in
organic material such as black coal-bearing smears and logs of partially petrified wood.
Coconinoite is the most common
U6+-bearing mineral at the mine and is found scattered throughout the
conglomerate, locally replacing organic debris.
Oswaldpeetersite occurs, associated with gypsum, along bedding planes
of a layer of siltstones within the
conglomerate. Additional associated minerals are
cuprite, antlerite,
goethite, lepidocrocite,
mbobomkulite,
hydrombobomkulite,
sklodowskite and two undefined
uranium minerals.
Oswaldpeetersite most commonly occurs as micrometric prismatic crystals arranged in radiating groups, rarely
distributed on layers of gypsum. The dimensions of the crystals are
approximately 0.1 x 0.01 x 0.002 mm3+
(CM 39.1685-1689).
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