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Historic photo : Excavating giant vivianite crystals by
local miners in the Anloua swamps, Cameroon

Photo Source : unknown

Giant Vivianite Crystals in the Anloua swamps, Cameroon

Coordinates : 7°25'N , 13°29'E : Anloua, N´gouandere, Cameroon

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- Giant Vivianite Crystals at Anloua -

 

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 vivianite crystals by far !

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

The vivianite crystals of Anloua, which form stellate aggregates of more than 2 meter (reportedly 4,5 meter !) in diameter with individual crystals reaching a maximum of 1,35 meter, are often somewhat rounded, probably due to corrosive effect of humic acids, and display a greyish blue colour.

Vivianite is a very common mineral in swamps and many localities are known. In fact most of the swamps in middle Europe harbour this iron phosphate, forming 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 hydro-enviroment such as a swamp or mire. In contrast to the above mentioned famous vivianite localities in Bolivia etc. the swamp vivianites rarely, if ever, form good crystals.However, this was the case in Anloua in Cameroon. The question remains, why that...?

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.

Anloua Vivianite in a Nutshell :


Mineralogy :

Vivianite

Crystal Size :

Individual prissmatic crystals of vivianite up to 1.35 meter and star aggregates up to 4.5 meter size


Geology & Origin :

Recent to subrecent in situ crystallisation in peat / swamp environs from iron and phosphorous rich solutions in acidic, anoxic millieu.


Current status :

unknown


Remarks :

A classic site of giant crystals, which apparently still produce vivianite specimen from time to time.

 

 

Resources and Relevant Weblinks :

For more information on the mineral vivianite please have a look at www.mindat.org, Webmineral and the german Mineralienatlas.

Surprisingly little information is published about this famous and classic locality, at least not in english language. Numerous mineralogical museums, e.g. the Ecole de Mines, Paris display some magnificient crystal clusters and single vivianite crystals from this locality. Further more, the Museum of the BRGM at Orleans, France shows a part of a truly giant vivianite rosette, originally measuring 4.5 meter in diameter !

 

 

 

Large vivianite crystal specimen from Anloua
Mineralogical Museum Strasbourg

Photo Source : Wikipedia

 

Anloua vivianite on display in the Ecole de Mines, Paris

Photo Source : Ecole de Mines

 

Detail of a vivianite crystal from Anloua
Fersman Museum, Russia

Photo Source : A.A.Ebseeb

 

Famous mineralogist Claude Guillemin
among Anloua vivianite crystals

Photo Source : unknown, about 1960

 

Vivianite crystal at Natural History Museum, Calci, Pisa, Italy

Photo Source : Thomas Krassmann

 

 

 

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