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Formula: Fe2+Fe3+5(PO4)4(OH)5.6H2O
Hydrated phosphate containing hydroxyl, beraunite group
Specific gravity: 2.94 measured, 2.907 calculated
Hardness: 3 to 4
Streak: Pale olive-green
Colour: Dark green to olive-green
Solubility: Dissolves easily in hydrochloric acid (35%), slowly in orthophosphoric acid (85%) and not at all in nitric acid
Environments
Pegmatites
Sedimentary environments
Although ferroberaunite was approved only in 2021, it is not a new mineral; previously it was called
beraunite, which now has been redefined as
Fe3+6(PO4)4(OH)4.6H2O
Localities
At the type locality, the Gravel Hill Mine, Perran Iron Lode, Perranzabuloe, Cornwall, England, UK, ferroberaunite
occurs in cavities of limonite iron ore.
Its flattened prismatic crystals up to 400 μm long are dark green to olive green, transparent to translucent, with a
vitreous lustre, pearly on cleavages
(MM 86.3.363-372).
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