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Formula: Ca2Fe3+3O2(AsO4)3.3H2O
Hydrated arsenate,
mitridatite group
Forms pseudomorphs after
siderite and
scorodite
Specific gravity: 3.60
Hardness: 4½, 1½ in fibres
Streak: ochre-yellow
Colour: Golden-yellow to yellow-brown, reddish-brown, brown, black; reddish brown to brownish yellow in
transmitted light
Solubility: Readily soluble in hot acids
Environments:
Arseniosiderite is a rare secondary mineral formed by the
low-temperature oxidation of earlier arsenic-bearing minerals, such as
scorodite,
arsenopyrite and
löllingite
(Webmin).
Associated Minerals at the type locality include quartz,
psilomelane, hematite and
goethite
(Mindat).
At Hūttenberg, Carinthia, Austria, arseniosiderite occurs in felted masses with
scorodite, symplesite,
pitticite and
pharmacolite on löllingite.
At Romanêche-Thorins, Saône et Loire, France, arseniosiderite occurs in a manganese deposit with
quartz, goethite,
romanèchite and
psilomelane
(Dana).
At Schneeberg, Bavaria, Germany, arseniosiderite occurs with
erythrite and
roselite
Dana.
At the Jesus Maria Mine, Mazapil district, Mexico, arseniosiderite occurs with
pharmacolite, chrysocolla and
calcite, and as pseudomorphs
after
scorodite.
(Dana)
At the Carrock mine, Caldbeck Fells, Cumbria, England, UK, arseniosiderite occurs as aggregates coating
quartz and arsenopyrite,
probably formed by the
alteration of scorodite
(C&S).
At Ingray Gill, Caldbeck Fells, Cumbria, England, UK, arseniosiderite occurs with
scorodite,
pharmacosiderite and
erythrite, and is almost
certainly derived from the alteration of erythrite
(C&S).
At Nether Row Brow, Caldbeck Fells, Cumbria, England, UK, arseniosiderite has been found with
scorodite, beudantite and
carminite, probably formed by the alteration of
scorodite
(C&S).
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