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Formula: Na6(UO2)2(SO4)5(H2O)7.1.5H2O
Valence: Na6(U6+O2)2(S6+O4)5(H2O)7.1.5H2O
Hydrated uranyl sulphate
Crystal system: Triclinic
Specific gravity:
Hardness: 2½
Streak: Pale green-yellow
Colour: Yellowish green to greenish yellow
Luminescence: Bright bluish-green fluorescence under long wave and short wave UV
Solubility: Easily soluble in water; slightly deliquescent.
Environments
Sedimentary environments
Hydrothermal environments
Ottohahnite was approved in 2015, but to date (April 2026) it has been reported only from the type locality
Localities
At the type locality, the Blue Lizard Mine, Red Canyon Mining District, San Juan County, Utah, USA,
klaprothite,
péligotite and ottohahnite
were found together as secondary phases. All three minerals
occur as yellowish-green to greenish-yellow crystals, are brittle with irregular fracture, have Mohs hardness of ∼2½
and exhibit bright bluish-green fluorescence, and all are easily soluble in room-temperature H2O. Only
klaprothite exhibits cleavage, perfect in two directions
(MM 81.4.753-779).
The minerals occur as efflorescent crusts on mine walls, formed by hydration-oxidation weathering of
primary uranium
minerals (mainly uraninite) by acidic solutions from the decomposition of
sulphides. Associated minerals include blödite,
bluelizardite, bobcookite,
epsomite, gypsum,
hexahydrite, konyaite,
plášilite and tamarugite
(HOM).
Ottohahnite from the Blue Lizard Mine -
Image
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