267 D33. Mineralogy/Crystallography (Posters)

Tuesday, 24 October 2017
9:00 AM - 6:30 PM
Halls 4EF

POVONDRAITE CRYSTAL CHEMISTRY

Paper number: 267-14
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The tourmaline super-group has a general chemical formula of XY3Z6 (T6O18) (BO3)3 V3W, and povondraite is a species of tourmaline with a formula of NaFe3+3(Fe3+4Mg2) Si6O18 (BO3)3 (OH)3O. Through standard normalization procedures, multiple researchers have reported quantities of greater than 1 apfu in the X-site in povondraite. Several different explanations for this anomaly have been explored, including incorrect Fe2+/Fe3+ ratios, [4]B, and OH+F sums. These could all change the normalized values, however they fail to explain the variance seen in povondraite, as any normalization scheme which would lower the X-site cation value also lowers all other cations, resulting in apparent vacancies in other cation sites, which has never been reported for tourmaline. We have collected S-XRD and TEM data on samples of povondraite and EMPA data from several different labs in order to try to isolate the cause of the reported anomaly.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-304683

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