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Comment on Lykova et al. (2024): “Natromelansonite, Na3Zr[Si7AlO19]⋅4–5H2O, a new member of the rhodesite mero-plesiotype series from Mont Saint-Hilaire, Quebec, Canada”

Published online by Cambridge University Press:  30 October 2024

Thomas E. Gore Open the ORCID record for Thomas E. Gore [Opens in a new window]  and
Andrew M. McDonald
Thomas E. Gore*
Affiliation:
Geoscience Laboratories, Ontario Geological Survey – Ministry of Mines, 933 Ramsey Lake Road, Sudbury, Ontario, Canada
Andrew M. McDonald
Affiliation:
Harquail School of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, Canada
*
Corresponding author: Thomas E. Gore; Email: [email protected]
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Abstract

In this communication, we present a brief response to Lykova et al. (2024) who, in a paper in volume 88 https://doi.org/10.1180/mgm.2024.1 (this journal), describe the occurrence of the new mineral natromelansonite, Na3Zr(Si7AlO19)⋅4–5H2O, and provide commentary on the related species, melansonite (Na,□)□2KZrSi8O19⋅5H2O. The comments in question revolve primarily around the roles and abundances of Al and Na in both minerals, and how their incorporation is best represented in their idealised formulae.

Lykova et al. (2024) state that Al is an essential component of both melansonite and natromelansonite and should thus be reflected in the ideal formulae. With respect to Na, they propose that the ideal formula of melansonite contains two Na apfu rather than one, as was presented in our initial definition of the mineral.

We reiterate there is no unequivocal evidence that Al is an essential component of melansonite, occupying a unique crystallographic site, but rather, it only substitutes for Si. Secondly, though the true Na content of melansonite is probably higher than were originally reported (this being simply explained by the thin nature of the crystals analysed and the volatility of Na under the electron beam), it cannot reconcile the doubling of the Na apfu for melansonite, as was suggested by Lykova et al. (2024).

Type
Comment
Information
Mineralogical Magazine , Volume 88 , Issue 5 , October 2024 , pp. 623 - 625
Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland

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References

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