5754 Biraite-(Ce), Hydroxylbastnasite-(Ce), Strontianite, Aragonite, Calcite, Cordylite-(Ce), Cordylite-(La), Niobochevkinite-(Ce), Ferriallanite-(Ce), Talc, Thorite, Daqingshanite-(Ce), Daqingshanite-(La), Ancylite-(Ce), Ancylite-(La), Kukharenkoite-(Ce), Carbocernaite, Cordilitovaya carbonatite vein, Ust’-Biraya deposit, Vitim Plateau, Eastern Siberia, Russia

Extremely rich 8x7x2mm specimen containing abundant inclusions (red arrowed) of brown biraite-(Ce) – an extremely rare silico-carbonate of REE. Biraite contains microscopic inclusions of hydroxylbastnasite-(Ce) and intergrows with its more yellow macro grains well recognisable under magnification (yellow arrowed). Light matrix of the sample represented by pale-greenish, apatite-like strontianite-aragonite with composition (Sr0.5Ca0.5)[CO3] and minor white calcite with typical rhombohedral cleavage. Very valuable addition to biraite in this sample are two complex Ba-Sr-REE carbonates – more brightly coloured cordylite-(Ce) (orange arrowed) and pale cordylite-(La) (pink arrowed). Abundant cordylite gave the name to this carbonatite vein. Another very worthy mineral of this specimen is well formed and complete crystal of black niobochevkinite-(Ce) (with Nb>>Ti) (blue arrowed). This mineral from the locality was recently described in two articles in American Mineralogist. Other minerals represented in the sample are: black ferriallanite-(Ce) (black arrowed), plates of marine green to pearly talc (green arrowed) and reddish-brown thorite (lilac arrowed). Also in the sample, microscopic invisible grains of daqingshanite-(Ce) and -(La), ancylite-(Ce) and -(La), kukharenkoite-(Ce) and carbocernaite. This is a third of minerals known in this remote and hard-accessible locality in a single sample. Note that for two of them (biraite-(Ce) and cordylite-(La)) it is Type Locality. And both them are author’s material. Includes SEM photo with marked place of analyses and EDX spectrum.

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