Rameauite is a hydrated complex uranyl oxide mineral with formula K₂Ca(UO₂)₆OH₁₆·H₂O or K₂CaU⁶⁺₆O₂₀·9(H₂O).

Crystallography

Rameauite has four observed forms which are {010}, {100}, {001} and {110}. The angles between these faces are {100}^{001} = 58°40' and {010}^{110} = 49° 50'. The crystals are always twinned on {100} and they are flattened parallel to {010} , and elongated parallel to {001}. The mineral rameauite is an example of a monoclinic mineral and appears pseudo-hexagonal. I has unit cell dimensions of: a= 13.97, b= 14.26, c= 14.22 with β = 121.02°.

Occurrence

It was first described in 1972 for an occurrence in the Margnac Mine, Compreignac

Compreignac

Compreignac is a commune in the Haute-Vienne department in the Limousin region in western France.-Geography:The commune covers 4,762 hectares. Compreignac is located to the north of the city of Limoges, approximately 10 minute travel along the Autoroute A20.Inhabitants are known as...

, Haute-Vienne

Haute-Vienne

Haute-Vienne is a French department named after the Vienne River. It is one of three departments that together constitute the French region of Limousin.The chief and largest city is Limoges...

, Limousin

Limousin (région)

Limousin is one of the 27 regions of France. It is composed of three départements: Corrèze, Creuse and the Haute-Vienne.Situated largely in the Massif Central, as of January 1st 2008, the Limousin comprised 740,743 inhabitants on nearly 17 000 km2, making it the second least populated region of...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and named after Jacques Rameau (1926 - 1960), French prospector at the "Commissariat à l'Energie Atomique", who discovered the deposit where the mineral occurs.
In addition to the type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 in France it has been reported from the Orphan Mine on the south rim of the Grand Canyon

Grand Canyon

The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...

 in Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

 and on Rhyolite Ridge, Esmeralda County, Nevada

Esmeralda County, Nevada

Esmeralda County is a county in the west of U.S. state of Nevada. Its county seat is Goldfield. Its 2000 census population was officially 971, making its population density 0.1045 inhabitants/km² , the second-lowest of any county-equivalent outside of Alaska. As of 2010, the population had...

.