Vivianite is a phosphate mineral of iron. It has the composition Fe3(PO4)28H2O . These samples are on display in the Smithsonian Museum of Natural History. This sample measures about 6x8 cm and is from Huanuni mine, Oruro, Bolivia.
This vivianite sample measures about 5x7 cm and is from Kamysh-Burunskiy mine, Kertch, Crimea Peninsula, Ukraine.