Beschreibung:
Kamotoïte-(Y) occurs as crusts of elongated bright yellow blades on uraninite matrix. Optically biaxial negative, 2Vcalc. = 87°, γ = 1.731, β = 1.667 and α = 1.604. Monoclinic, space group P21/a, a = 21.22(1), b = 12.93(1), c = 12.39(1) Å, β = 115.3(1)°, Z = 4, dcalc. = 3.94, dmes. = 3.93. Strongest lines in the X-ray powder pattern | d(Å), I, hkl | 6.48 (10) 020, 8.49 (8) 011, 3.054 (6) 402, 40-4 , 3.49 (4) 222 , 22-3, 2.762 (4) 422, 42-4. An analysis with the electron microprobe gave : UO3 63.39, Y2O3 6. 19, Nd2O3 2.36, Gd2O3 2.10, Sm2O3 1.91, Dy2O3 1.64, CO2 (by chromatography) 7.24, H2O (difference between loss at 800 °C and % CO2) 14.30, total 99.13 %. Formula : 4 UO3 (Y,Nd,Gd,Sm,Dy)2O3. 3 CO2. 14.5 H2O. The mineral was found in the Cu-Co deposit of Kamoto, southern Shaba, Zaïre. The name is for the locality.
La kamotoïte-(Y) se présente en encroûtements de tablettes allongées jaune vif sur l'uraninite. Optiquement biaxe négative, 2Vcalc. = 87°, ng = 1,731, nm = 1,667 et np = 1,604. Système monoclinique, groupe spatial P21/a, a = 21,22(1), b = 12,93(1), c = 12,39(1) Å, β = 115,3(1)°, Z = 4, dcalc. = 3,94, dmes. = 3,93. Raies principales du diagramme de poudre | d(Å), I, hkl | 6,48 (10) 020, 8,49 (8) 011, 3,054 (6) 402, 40-4 , 3,49 (4) 222 , 22-3, 2,762 (4) 422, 42-4. Analyse chimique à la microsonde électronique UO3 63,39, Y2O3 6, 19, Nd2O3 2,36, Gd2O3 2,10, Sm2O3 1,91, Dy2O3 1,64, CO2 (par chromatographie) 7,24, H2O (différence entre P. F. 800° et % CO2) 14,30, total 99,13 %. Formule : 4UO3. (Y,Nd,Gd,Sm,Dy)2O3. 3CO2. 14,5H2O. Le minéral provient du gisement cupro-cobaltifère de Kamoto au Shaba méridional. Le nom rappelle la provenance.