Bastnäsite-(Nd), a new Nd-dominant member of the bastnäsite group from the Stetind pegmatite, Tysfjord, Nordland, Norway

Bastnasite-(Nd), ideally (Nd,La,Ce)(CO 3 )F, occurs in the Stetind pegmatite, Tysfjord, Nordland, Norway, in association with bastnasite-(Ce), calcioancylite-(Nd) and/or kozoite-(Nd), stetindite, vyuntspakhkite-(Y) and Y-bearing fluorite. It forms 20 μm wide zones in outer parts of tabular bastnasite-(Ce) crystals. Bastnasite-(Nd) is translucent and is pale purplish pink to colourless with a vitreous, greasy or pearly lustre. Bastnasite-(Nd) has a Mohs hardness of 4–4½, is brittle, and shows an indistinct cleavage on {1010} and an uneven fracture. The calculated density and mean refractive index are 5.23 g cm −3 and 1.76, respectively. It is hexagonal, space group P 62 c , a = 7.0792(13), c = 9.721(2) A, V = 421.92(18) A 3 and Z = 6. The five strongest lines in the powder XRD pattern are [ d (A), I / I 0 , hkl ]: 4.86, 71, 002; 3.54, 70, 110; 2.86, 100, 112; 2.04, 31, 300 and 2.00, 48, 114. The electron-microprobe analyses lead to the empirical formula (on the basis of M = C = 1 apfu ): Nd 0.353 La 0.253 Ce 0.251 Pr 0.086 Sm 0.037 Gd 0.016 Y 0.004 Dy 0.001 CO 2.978 F 1.044 . Bastnasite-(Nd) is a member of the bastnasite group, and is the Nd-dominant analogue of bastnasite-(Ce), bastnasite-(La) and bastnasite-(Y). Bastnasite-(Nd) formed as a late phase in cavities in Y-bearing fluorite, which in turn is a late formation of the pegmatite.