Les phosphates d'uranyle et d'aluminium de Kobokobo. V. La mundite, nouveau minéral

Abstract

Mundite occurs at Kobokobo, Kivu, Zaïre, as yellow tablets flattened on {010}. 3 perfect cleavages {010}, {100} and {001}. Orthorhombic. Space group P2₁cn or Pmcn with a = 17.08 Å, b = 30.98 Å and c = 13.76 Å. Z = 16. Density (calc.) = 4.295 Mg/m³. The strongest lines of the X-ray powder pattern are 7.80 Å (100) 040, 3.37 Å (70) 024 and 163, 3.87 Å (60) 080 and 3.06 Å (50) 502. Optically biaxial negative, 2V = 33°. ng = 1.688, nm = 1.682 and np (calc.) = 1.62. a = Z, b = X and c = Y. Formula is Al (UO₂)₃ (PO₄)₂ (OH)₃ • ~ 5,5 H₂O. Structural group of phosphuranylite.