Portal de Periódicos da CAPES

Hydroxyl-bastnaesite-(Nd), a new mineral from Montenegro, Yugoslavia

1985; Cambridge University Press; Volume: 49; Issue: 354 Linguagem: Inglês

10.1180/minmag.1985.049.354.11

1471-8022

Zoran Maksimović, György Pantó,

Geochemistry and Elemental Analysis

Abstract Hydroxyl-bastnaesite-(Nd), the Nd- and OH-dominant new member of the bastnaesite group, has been found in the red karstic bauxites near Nikšić, Montenegro. It occurs as whitish, irregular aggregates of crystals usually 100–200 µ m in diameter. Hexagonal with the cell dimensions a = 7.191 and c = 9.921 Å, with Z = 6. The strongest lines of the X-ray powder diffraction pattern ( d, I, hkl ) are: 4.95 80(002); 3.596 79(110); 2.911 100(112); 2.077 29(300); 2.042 51(114); 1.914 30(302). The mineral is uniaxial positive, ω 1.715, ɛ 1.81; D calc 4.89 g/cm 3 . Electron probe analysis, using garnet, apatite and synthetic glass standards, combined with thermogravimetric and evolved gas analysis, gave Y 2 O 3 0.2, La 2 O 3 27.1, Ce 2 O 3 0.3, Pr 2 O 3 8.5, Nd 2 O 3 31.5, Sm 2 O 3 4.4, Eu 2 O 3 1.3, Gd 2 O 3 1.4, CaO 0.3, F 3.3, H 2 O 2.26, CO 2 20.63, sum 101.19, less O = F 1.39, total 99.80%. This analysis calculates to (Nd 0.41 La 0.36 Pr 0.11 Sm 0.06 Gd 0.02 Eu 0.02 Ca 0.01 ) Σ0.99 (CO 3 ) 1.03 [(OH) 0.55 F 0.38 ] Σ0.93 , or ideally, (Nd,La)CO 3 (OH,F), with Nd > La and OH > F.