A blue sodic beryl from Southeast Ireland

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Authors:Sanders, I. S.; Doff, D. H.
Author Affiliations:Primary:
Trinity Coll., Dep. Geol., Dublin, Ireland
Volume Title:Mineralogical Magazine
Source:Mineralogical Magazine, 55(379), p.167-172. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Publication Date:1991
Note:In English. 18 refs.; illus. incl. 2 tables
Summary:Deep azure-blue beryl is reported from veins in Upper Devonian conglomerate from southeast Ireland. Microprobe analysis, Mössbauer spectroscopy and loss on ignition suggest an unusual chemistry with an exceptionally high degree of substitution of Fe and Mg for Al, and extreme amounts of Na and water held within channel sites in the structure. The calculated structural formula is: Be2.94(Al1.26Fe0.153+Fe0.162+Mg0.42)Si6.07O18[Na0.45(H2O)0.95] Refractive indices (1.603 and 1.595) and the cell edge, a, (9.292 Å) are also unusually high. Colourless beryl from the same locality, some of which forms cores to blue beryl prisms, has less octahedral substitution and a lower Fe/Mg ratio. The origin of the beryl is tentatively linked to contemporaneous volcanic activity.
Subjects:Beryl; Devonian; Mineralogy; Minerals; Occurrence; Paleozoic; Ring silicates; Silicates; Upper Devonian; Europe; Ireland; Western Europe; Southeastern Ireland
Abstract Numbers:91M/4626
Record ID:1991041114
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
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