Quick answer: because bones and bodies are full of phosphate, and vivianite is simply iron phosphate. When remains lie in waterlogged, oxygen-poor ground with a source of iron (iron-rich soil, an iron coffin, a corroding aircraft), the phosphate and dissolved iron combine into vivianite crystals on the bones, teeth, and skin. It starts nearly colorless and turns progressively deeper blue once air reaches it.
The recipe
- Phosphate: from decaying bone, teeth, and tissue.
- Iron: from soil, groundwater, or nearby iron objects.
- Water and no oxygen: waterlogged, anaerobic ground keeps iron in its dissolved ferrous (Fe2+) form. Bacteria help by releasing iron and phosphate and influencing crystal shape (Atlas Obscura).
Vivianite has been found as crusts on bone, needle-like crystals in teeth, blotches on skin, and even on adipocere, the waxy “grave wax” that forms from body fat in wet burials (Atlas Obscura).
Real cases
- John White, England (buried 1861): a railway engineer buried in a cast iron coffin with a glass viewing window. Groundwater got in, and when the coffin was exhumed over a century later, his body was covered in blue crystals (Atlas Obscura).
- A B-26B crew, South Vietnam (1963): an American aircraft went down in the mountains. When the crew’s remains were recovered decades later, investigators first thought the blue on the bones was paint. It was vivianite, fed by iron from the corroding plane (Atlas Obscura).
- Seven Years’ War soldiers, near Liberec, Czech Republic (1757): the blue crust on their bones interfered with DNA analysis, so researchers had to develop a new extraction method for vivianite-coated bone (Atlas Obscura).
- North Brisbane Burial Grounds, Australia: excavation found vivianite in 25 graves. The coating appears to have slowed decay, and it corroborated a historical newspaper report of flooding at the cemetery (Atlas Obscura).
- Ötzi the Iceman (about 5,000 years old): his skin has blue vivianite spots where it touched iron-bearing rock (Atlas Obscura).
Why your vivianite crystal darkens
Fresh vivianite crystals can be nearly colorless to pale green. Light and air oxidize some of the iron from Fe2+ to Fe3+, and the interaction between the two forms of iron absorbs red light, pushing the color toward deep blue-green and eventually near-black. Bodies follow the same rule: crystals are pale underground and “will rapidly turn progressively darker shades of blue” on exposure (Atlas Obscura). That’s why collectors store vivianite in the dark. More in Vivianite: the crystal that changes color when you look at it.
Where the big crystals come from
The same chemistry, minus the grim part, makes collector specimens: vivianite grows inside fossil shells, bog iron, and phosphate-rich sediments. Some of the finest crystals ever found come from the tin mines of Bolivia and phosphate-rich clays in Cameroon and Brazil. The mineral was named for John Henry Vivian, a Welsh-Cornish mineralogist.
FAQ
Is vivianite toxic? No more than other iron phosphates; it’s very soft (Mohs 1.5-2), so handle gently. See Toxic minerals: what actually needs care.
Do copper objects do something similar? Yes. Bullet jackets, buttons, and jewelry can stain buried bone green with copper minerals (Atlas Obscura).
Related reading
- Ghost bands, glowing rocks and fossilized wood
- Pseudomorphs
- Which crystals should not be stored together
Related pieces in the shop
Source: Atlas Obscura, “The Blue Mineral That Grows on Human Remains”; ScienceAlert, “Vivianite, the blue mineral that turns buried bodies blue.”
