Formula: Fe3+(PO4).2H2O
Hydrated normal phosphate, metavariscite group, dimorph of strengite
Specific gravity: 2.74 to 2.76
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)


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

Common impurities: Al,Mn

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