There are some localities in the world, which have supplied large and often beautiful crystals of Vivianite : Llallagua in Bolivia is one of them, Cornwall and Kertsch on the Krim peninsula are others, but Anloua in Cameroon supplied the largest by far.

The vivianite crystals in Anloua were discovered by chance by some local farmers around 1920, but were soon systematically excavated under french colonial supervision (see image above). Indeed this operation managed to obtain some very large and almost undamaged vivianite crystals, which are ever since on display in the famous Ecole de Mines (now : MINES ParisTech) in Paris.

Large vivianite crystal specimen from Anloua
Collection Ecole de Mines (now : MINES ParisTech), Paris

Photo: Thomas Krassmann

The vivianite crystals of Anloua, which form stellate aggregates of more than 2 m diameter and individual crystals of a maximum size of 1,35 meter, are often somewhat rounded due to corrosive effect of humic acids (?) and display a greyish blue colour on surface. Only when backlit, they show their true magnficient bluish green colour.

Vivianite is a very common mineral in swamps and many localities are known - in fact most of the swamps in middle Europe - where this iron phosphate forms white earthy masses and crusts, which rapidly turn bright blue when exposed to fresh air. This is the so called "Blaueisenerz" (blue iron ore) which forms by interaction of iron and phosphorous rich solutions in an acidic, oxygen poor bogland enviroment.

In contrast to the above mentioned famous vivianite localities in Bolivia etc. the swamp vivianite rarely, if ever, form large crystals. However, this was the case in Anloua in Cameroon. Obviously there must have been a surplus of phosphate in the Anloua swamps, possibly derived from underlying phosphate rich rocks.

Even if the giant vivianite crystal finds of Anloua seems to be long gone history, the locality still produces vivianite specimen, which can be found from time to time on mineral fairs, mostly in form of thin, bladelike translucent cleavage fragments up to about 40 cm size.