Rameauite

Rameauite is a hydrated complex uranyl oxide mineral with formula K2Ca(UO2)6OH16·H2O[4] or K2CaU6+6O20·9H2O.[3]

Rameauite
General
CategoryOxide mineral
Formula
(repeating unit)		K2Ca(UO2)6OH16·H2O or K2CaU6+6O20·9H2O
Strunz classification4.GB.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella= 13.97 Å, b= 14.26 Å
c= 14.22 Å, β = 121.02°: Z = 4
Identification
Formula mass2,028.57 g/mol
ColorOrange
Crystal habitPrismatic and/or can consist of a hexagonal outline
TwinningOn {100}
CleavageGood cleavage
DiaphaneitySemitransparent
Density5.6
Optical propertiesBiaxial Negative
Refractive indexa= n.d. β= 1.95 γ= 1.97
2V angle32° (meas.)
Other characteristics Radioactive
References[1][2][3]

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°.[3][5]

Occurrence

It was first described in 1972 for an occurrence in the Margnac Mine, Compreignac, Haute-Vienne, Limousin, 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.[3][4] In addition to the type locality in France it has been reported from the Orphan Mine on the south rim of the Grand Canyon in Arizona and on Rhyolite Ridge, Esmeralda County, Nevada.[4]

References
  1. http://webmineral.com/data/Rameauite.shtml
  2. http://un2sg4.unige.ch/athena/cgi-bin/minfich?s=Rameauite
  3. Handbook of Mineralogy
  4. Mindat.org
  5. Cesbron, F., W.L. Brown, P. Bariand, and J. Geffroy (1972) Rameauite and agrinierite, two new hydrated complex uranyl oxides from Margnac, France. Mineralogical Magazine, 38, 781–789.
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