Vivianite
“Colorless when fresh, deep blue in light”
Vivianite is an iron phosphate mineral with a remarkable property — freshly exposed crystals are colorless or pale green, but they rapidly darken to a deep indigo-blue or even black upon exposure to light. This dramatic color change is caused by the oxidation of iron within the crystal structure.
iron(II) phosphate hydrate (Fe₃(PO₄)₂·8H₂O)
Morococala Mine (Bolivia), Cameroon, Kerch Peninsula (Crimea), Tomokoni (Bolivia), Big Fish River (Yukon, Canada)
1.5-2
Vivianite crystals have been found forming on human bones in waterlogged archaeological sites — iron from the bones combines with phosphate to grow eerie blue crystals directly on ancient skeletons.
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