Phosphosiderite

barbosalite

strengite

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Formula: Fe3+(PO4).2H2O
Hydrated normal phosphate, metavariscite group, paramorph of strengite
Crystal System: Monoclinic
Specific gravity: 2.74 to 2.76 measured, 2.72 calculated
Hardness: 3½ to 4
Streak: White
Colour: Purple to reddish violet, rose-red, peachy-pink, brownish yellow, moss-green, colourless; rose to colourless in transmitted light.
Solubility: Totally soluble in hydrochloric acid, nearly insoluble in nitric acid (Mindat)
Common impurities: Al,Mn
Environments:

Pegmatites

Phosphosiderite is typically an alteration product of triphylite in zoned complex granite pegmatites; it also may be a component of soils, replacing bones or shells. Associated minerals include triphylite, barbosalite, leucophosphite, laueite, hureaulite, strengite and turquoise (HOM).

At the phosphate deposits of South Australia, phosphosiderite is associated with variscite, quartz and leucophosphite (AJM 17.1.25).

At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the pegmatites are beryl-type rare-element (RE) pegmatites.
The Number 1 mine exposed a pegmatite that shows the most complex zonation and diverse mineralogy of any of the Keyes pegmatites. Six zones are distinguished, as follows, proceeding inward from the margins of the pegmatite:
(1) quartz-muscovite-plagioclase border zone, 2.5 to 30.5 cm thick
(2) plagioclase-quartz-muscovite wall zone, 0.3 to 2.4 metres thick
(3) plagioclase-quartz-perthite-biotite outer intermediate zone, 0.3 to 5.2 metres thick, with lesser muscovite
(4) quartz-plagioclase-muscovite middle intermediate zone, 15.2 to 61.0 cm thick
(5) perthite-quartz inner intermediate zone, 0.9 to 4.6 meters thick
(6) quartz core, 1.5 to 3.0 metres across
The inner and outer intermediate zones contained perthite crystals up to 1.2 meters in size that were altered to vuggy albite-muscovite with fluorapatite crystals. This unit presumably was the source of the albite, muscovite, fluorapatite, quartz and other crystallised minerals found in pieces of vuggy albite rock on the dumps next to the mine.
The middle intermediate zone produced sheet mica with accessory minerals including tourmaline, graftonite, triphylite, vivianite, pyrite, pyrrhotite, and beryl crystals to 30.5 cm long and 12.7 cm across.
Phosphosiderite occurs here associated with rockbridgeite (R&M 97.4.322).

At the type locality, the Kalterborn Mine, Eiserfeld, North Rhine-Westphalia, Germany, phosphosiderite occurs in iron ore (Dana).

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