Syenite, Eudialyte. Kola Russia

This is a thin section microscope slide of a Eydialyte Syenite from the Lovozero alkali intrusiuon, Kola Peninsular in Russia. An identification challenge! The matrix is a granular mass of colourless crystals, some showing excellent crystal shape. These are either nepheline or sanidine (or both). It is usually not too difficult to identify these, but sometimes they do not show the features eg twinning for sanidine, that enable the two minerals to be separated. The crystals are full of minute aegirine inclusions, eudialyte is present in very pale pink intersital areas (PPL) patchy grey XPL. Black phenocrysts of roughly square section that are brown on thin edges are also yet to be identified.


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