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Formula:
[Mn(H2O)6][☐As3+3Fe3+3(PO4)2O7]
Hydrated phosphate, walentaite subgroup,
walentaite group
Crystal System: Orthorhombic
Specific gravity: 2.72 measured, 2.72 calculated
Hardness: 3
Streak: Pale yellow
Colour: Bright yellow
Luminescence: Not fluorescent under UV
Environments
Pegmatites
Hydrothermal environments
Localities
At the Griffins Find Gold Mine, Lake Grace Shire, Western Australia, walentaite occurs as a
secondary mineral in the oxidised zone of the gold mine that
is hosted by granulite. Associated minerals include
pharmacosiderite,
jarosite and iron oxides
(HOM).
A the type locality, the White Elephant Mine, Cicero Peak, Pringle, Custer Mining District, Custer County, South
Dakota, USA, walentaite occurs as a rare secondary
mineral forming rosette-like aggregates of thin, bladed crystals approximately 20 x 60 x 1-2 µm3 in size.
It can also occur as coatings on other minerals. The walentaite occurs in several distinct parageneses in a
portion of the mine, where primary phosphates and
arsenides have been extensively altered. Associated minerals include
frondelite, rockbridgeite,
löllingite, spessartine,
quartz, tridymite and
muscovite.
Based on its occurrence with tridymite, it is suggested that
walentaite and its associated secondary phosphates
were not derived by interaction of primary phosphates with
late-stage pegmatitic fluids; rather, they apparently
originated due to the interaction of supergene solutions with
primary phosphates at relatively recent times when erosion
caused the pegmatite to interact with near-surface waters
(AM 69.1194).
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