• journal_title：European Journal of Mineralogy
• Contributor：Nenad Tomašić ; Andreja Gajović ; Vladimir Bermanec ; Maša Rajić Linarić ; Dangsheng Su ; Radek Škoda
• Publisher：E. Schweizerbart'sche Verlagsbuchhandlung Science Publishers
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.1127/0935-1221/2010/0022-2032
• journal_abbrev：Eur J Mineral
• issn：0935-1221
• volume：22
• issue：3
• firstpage：435
• section：Articles

Relics of the original samarskite structure were identified in a metamict ABO₄ mineral from Beinmyr pegmatite, Norway, using selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The chemical composition of the sample confirmed the affiliation to the samarskite group giving the general formula (REE_0.322Ca_0.269Fe_0.231U_0.142Mn_0.031Pb_0.011Th_0.010Zr_0.010Al_0.004Sc_0.002Na_0.001K_0.001)_∑1.034(Nb_0.707Ta_0.267Ti_0.069W_0.017Sn_0.007)_∑1.067O₄. The structure identified by transmission electron microscopy (TEM) techniques is well related to the orthorhombic low-temperature samarskite modification with cell parameters a = 5.68(1), b = 4.94(1), c = 5.24(2) Å. The observed diffraction maxima conform well to Pbcn space group. The untreated sample is X-ray amorphous. Gradual recrystallisation in air from 400 to 1000 °C yielded a pyrochlore phase being stable at all experimental temperatures. At 800 °C a high-temperature samarskite phase (s.g. P2/c) co-crystallised, with an increase in crystallinity at 1000 °C. Recrystallisation in a reducing atmosphere (Ar/H₂) did not yield the high-temperature samarskite phase solely. Unsuccessful recrystallisation of the high-temperature samarskite modification is mainly related to an alteration which shifted the composition of samarskite to pyrochlore, as shown by the occurrence of altered domains in the sample.