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Formula: Fe2+Fe3+2(AsO4)2(OH)2.4H2O
Hydrated arsenate,
arthurite group
Crystal System: Monoclinic
Specific gravity: 3.15 measured, 3.193 calculated for the empirical formula
Hardness: 3
Streak: Greenish yellow
Colour: Blackish green to dark brownish
Luminescence: No fluorescence under UV
Solubility: Dissolves in hot dilute hydrochloric or nitric acid but not in cold acids
Environments
Pegmatites
Hydrothermal environments
Bendadaite has been found on dumps of phosphate-bearing
columbite-beryl
pegmatite; it is a
secondary (or late hydrothermal) mineral with Fe and As derived
from weathered arsenopyrite
(HOM).
Localities
There are two co-type localities, the Almerindo mine, Linópolis, Divino das Laranjeiras, Minas Gerais, Brazil, and the
Bendada Mines, Bendada, Sabugal, Guarda, Portugal.
At the Almerindo mine, Linópolis, Divino das Laranjeiras, Minas Gerais, Brazil, bendadaite occurs in the
granite
pegmatite associated with
albite, muscovite,
quartz, schorl,
elbaite, löllingite,
scorodite, pharmacosiderite,
saléeite, phosphuranylite,
arsenopyrite, erythrite,
pharmacosiderite,
parasymplesite, karibibite,
scorodite and limonite
(HOM).
Bendadaite from the Almerindo Mine -
Image
At the Bendada Mines, Bendada, Sabugal, Guarda, Portugal, bendadaite was found as a weathering product of
arsenopyrite on a single hand specimen from the phosphate
pegmatite. Type bendadaite occurs as blackish green to
dark brownish tufts, less than 0.1 mm long, and flattened radiating aggregates, in intimate association with an
intermediate member of the
scorodite–mansfieldite series
(MM 74.3.469-486).
It is also associated with gypsum
(HOM).
Bendadaite from the Bendada Mines - Image.
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