Santabarbaraite is an amorphous ferric hydroxy phosphate mineral hydrate that was discovered in Tuscany, Italy in 2000. It also can be found in Victoria, Australia and Lake Baikal, Siberia. This phosphate mineral has a simplified formula Fe₃⁺³(PO₄)₂(OH)₃·5H₂O, which is the same formula of another non-amorphous phosphate mineral called allanpringite. Santabarbaraite occurs as pseudomorphic masses after vivianite (Fe₂⁺³(PO₄)₂·8H₂O). In the process, monoclinic vivianite oxidizes to form the amorphous santabarbaraite. Pseudomorphism can be seen in Victoria, Australia in Wannon Falls which is originally a well-known locality for vivianite and at Lake Baikal, Siberia where the oxidized santabarbaraite can be seen as a rim surrounding vivianite due to exposure to air.