Strengite is a relatively rare iron phosphate mineral with the formula: FePO₄·2H₂O. The mineral is named after the German mineralogist (1830–1897). Lavender, pink or purple in hue, it is similar to variscite and is partially soluble, particularly in conditions where there is a low pH and low oxidation-reduction potential. The color comes from ferric ion (Fe³⁺).

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Phosphate minerals Orthorhombic minerals Minerals in space group 61 {{Phosphate-mineral-stub