Strengite
Strengite is a relatively rare iron phosphate mineral with the formula: FePO4·2H2O.[5] The mineral is named after the German mineralogist Johann August Streng (1830–1897).[6] Lavender, pink or purple in hue, it is similar to variscite[7] and is partially soluble, particularly in conditions where there is a low pH and low oxidation-reduction potential.[5] The color comes from ferric ion (Fe3+).[8]