VIVIANITE

Vivianite (Fe(II)3(PO4)2·8H2O) is a hydrated iron(II) phosphate mineral that occurs in various geological settings. Its structure can incorporate small quantities of manganese (Mn2+), magnesium (Mg2+), and calcium (Ca2+) in place of iron (Fe2+). While pure vivianite is colorless, it readily oxidizes, resulting in a color change, and is typically observed as deep blue to bluish-green prismatic or flattened crystals. These crystals are frequently found within fossil shells, such as those of bivalves and gastropods, or attached to fossilized bone. Additionally, vivianite may form on iron coffins or human remains due to chemical reactions between the decomposing body and the iron enclosure.

The mineral was named in 1817 by Abraham Gottlob Werner, recognized as the "father of German geology," shortly before his death. The name honors either John Henry Vivian, a Welsh-Cornish politician and mineralogist from Truro, Cornwall, or Jeffrey G. Vivian, an English mineralogist. Vivianite was first identified at Wheal Kind in St Agnes, Cornwall.