Behoite and mimetite from the Saharjok alkaline intrusion,Kola Peninsula |
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Authors: | L M Lyalina Ye E Savchenko E A Selivanova D R Zozulya |
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Institution: | 1.Geological Institute, Kola Scientific Center,Russian Academy of Sciences,Apatity,Russia |
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Abstract: | The detailed study of the mineral composition of the nepheline syenite pegmatite from the Saharjok Intrusion has resulted
in the finding of behoite and mimetite, a mineral species identified in the Kola region for the first time. The pegmatite
body at the contact between nepheline syenite and essexite is unusual in textural and structural features and combination
of mineral assemblages including unique beryllium mineralization. Behoite Be(OH)2 is an extremely rare beryllium mineral. It occurs as powderlike aggregates in the leaching cavities between euhedral pyroxene
crystals. Behoite was identified by comparison of X-ray powder diffraction data of the studied mineral phase and behoite from
the Be-bearing tuff in the type locality of this mineral (Utah, United States). Mimetite was found in the same pegmatite of
the Saharjok intrusion. It forms unusual parallel-fibrous aggregates with individual fibers as long as ∼1 mm and only ∼1 μm
across. X-ray powder diffraction data and the chemical composition characterize the mineral as hexagonal phase Pb5AsO4]3Cl. Both behoite and mimetite are the products of late hydrothermal alteration of primary minerals (meliphanite, galena, arsenopyrite,
and loellingite). The secondary phases freely crystallized in the cavities remaining after the leached nepheline. |
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