Vivianite on Mammoth Tusk (Mammuthus primigenius)
Pamir Peninsula, Siberia

Like teeth of other mammals, the tusks of mammoths are made up of enamel externally and dentin internally. The latter is a calcareous substance composed of hydroxyappetite similar to bone but softer and chemically more active. Vivianite is the most common colored mineral associated with this substance, being a hydrated ferrous phosphate, vivianite and dentin share phosphate groups making it relatively easy for vivianite to form thin coatings on the damaged surfaces of fossilizing tusks.
Copyright © 2003 Giraud Foster & Norman Barker