Formula: Ba0.5Fe3+4(AsO4)3(OH)4.5H2O
Hydrated arsenate containing hydroxyl, pharmacosiderite group
Crystal System: Tetragonal
Specific gravity: 3.05 measured, 3.07 calculated
Hardness: 2½
Colour: Brown, yellow, reddish brown, green, bluish
Solubility: Readily soluble in warm 1:1 hydrochloric acid (Dana)

Hydrothermal environments


At Sunny Corner, New South Wales, Australia, occasionally bariopharmacosiderite forms in thin crusts in voids in beudantite - scorodite ore. Layers of goethite between separate generations of bariopharmacosiderite indicate alternating goethite and bariopharmacosiderite mineralising events, after the beudantite and scorodite had formed. Minor secondary baryte is also found in association with bariopharmacosiderite and tiny crystals of bariopharmacosiderite associated with native sulphur have been in voids after arsenopyrite in rock on a mine dump (AJM 17.1.48).

At the type locality, the Clara mine, Oberwolfach, Ortenaukreis, Freiburg Region, Baden-Württemberg, Germany, bariopharmacosiderite occurs on limonite and baryte (Dana).

At Burdell Gill, Caldbeck Fells, Cumbria, England, UK, bariopharmacosiderite is associated with rhodochrosite, and vivianite is often associated with corroded bariopharmacosiderite (JRS 8(1).1-9)

At Roughton Gill, Caldbeck Fells, Cumbria, England, UK, bariopharmacosiderite occurs in thin fractures in iron and manganese oxide rich wallrock and is often partially coated by iron oxide. Crystals and occasional anhedral masses of bariopharmacosiderite with beudantite and carminite have been collected from scree blocks near to the main vein exposure (JRS 11.7).

At Short Grain, Caldbeck Fells, Cumbria, England, UK, minute crystals of bariopharmacosiderite occur with arseniosiderite, beudantite and mimetite in quartz - baryte veinstone. Primary baryte is likely to have provided the barium ions required for bariopharmacosiderite to crystallise (JRS 12.51).

At the Tintic Mining District, Juab County, Utah, USA, bariopharmacosiderite has been found at the Centennial Eureka mine both as single cubic crystals and as druses on quartz. It occurs associated with arseniosiderite, azurite, beudantite, clinoclase, scorodite and tyrolite.
At the North Star mine, it usually occurs on quartz or goethite, with associations of baryte, enargite, mixite, olivenite, pyrite and volborthite. Individual cubic crystals measure only a few hundred microns, but druses of these crystals may cover up to a few square centimeters on matrix.
Single cubes of bariopharmacosiderite isolated on quartz also have been found at the North Star mine (MinRec 55.2.183-184).

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