Strengite
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Strengite is a relatively rare iron phosphate mineral with the formula: FePO₄·2H₂O. The mineral is named after the German mineralogist Johann August Streng. Wikipedia
Color: Colorless, pale violet, deep violet, red, carmine red, greenish white
Crystal class: Dipyramidal (mmm); H-M Symbol: (2/m 2/m 2/m)
Crystal habit: Botryoidal, radial, spherical
Crystal system: Orthorhombic
Formula mass: 186.85 g/mol
Formula (repeating unit): FePO4·2H2O
Mohs scale hardness: 3.5–4