07/04/2026
Vivianite forms on dead bodies when phosphate from decaying bones and teeth reacts with iron and groundwater in low-oxygen environments, such as waterlogged bogs or iron coffins.
When a body decomposes, anaerobic bacteria break down tissues and release phosphorus and iron. In the absence of oxygen and the presence of moisture, these elements bond to form the mineral vivianite (hydrated iron phosphate).
Vivianite is unique because it is one of the few minerals that is completely colorless when freshly formed but darkens dramatically and irreversibly when exposed to light and oxygen. This striking color shift, known as photo-oxidation, is driven by a fascinating chemical process: When photons of light hit the freshly exposed crystal, they cause an electron to shift. This causes iron atoms within the crystal structure to oxidize from ferrous iron (Fe²⁺) to ferric iron (Fe³⁺).
As this oxidation spreads, the mineral visibly morphs, transforming from transparent to opaque in a matter of hours or days. It shifts from clear or pale green to brilliant shades of turquoise and deep blue, eventually darkening into emerald green, purple, and finally an opaque black or indigo.
Because vivianite forms in oxygen-poor, iron-rich, and phosphate-rich environments, it is often found growing inside decomposing organic matter—such as fossilized teeth, shells, and decayed wood.
Pretty cool stuff!
