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4Al2O3 · H2O
A synonym of Akdalaite
Considered invalid mineral name by the CNMMN. The name akdalaite was substituted for "tohdite" in some publications (e.g., Tilley & Eggleton 1996); however, a mineral likely to be "tohdite" was recently recognized by the CNMMN (Burke & Ferraris 2005). In the latest turn of events, it has been shown that akdalaite has the same properties as synthetic and natural "tohdite." "Tohdite" is pending formal discreditation. (Rosenberg 2006).

Proposal IMA2004-051, hydrous alumina, was approved by the CNMMN (see publications "Minerals approved in 2004"). Several CNMMN members had asked, however, for a reexamination of akdalaite (69-002) which was approved as the first natural hydrous alumina.

The authors of 2004-051 obtained holotype material of akdalaite from the Fersman museum in Moscow, and the re-examination showed that akdalaite and the material for 2004-051 are identical. The previously refined unit cell of akdalaite is incorrect, so that akdalaite and 2004-051 are actually the same mineral species. The name akdalaite has priority; the fact that akdalaite was given a wrong space group does not necessitate a formal redefinition of this mineral. The re-examination and 2004-051 should be published as “New data and a new
occurrence of akdalaite”. The approval decision of the CNMMN on 2004-051 is consequently nullified.

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References for TohditeHide

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Yamaguchi, G., Yanagida, H., and Shuitiro, O. (1964a) new alumina hydrate, "tohdite" (5Al2O3·H2O) Bull. Chem. Soc. Japan: 37: 752-754.
Yamaguchi, G., Yanagida, H., and Shuitiro, O. (1964b) The crystal structure of tohdite. Bull. Chem. Soc. Japan: 37: 1555-1557.

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