Hochleitner, Rupert; Fehr, K. T.
The keckite problem and its bearing on the crystal chemistry of the jahnsite group: Mössbauer and electron-microprobe studies.
In: Canadian Mineralogist, Vol. 48, No. 6: pp. 1445-1453
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Keckite is considered to be a member of the jahnsite group, though the formula originally given does not conform to the general formula of minerals of that group. In this study, samples of keckite from different localities, including the type locality, have been investigated. Keckite is a special member of the jahnsite group containing trivalent iron not only at the C site but also at the B site, as proven by Mössbauer spectroscopy. The chemical composition was determined by electron-microprobe analysis, and the H 2O content, by differential thermogravimetry. A new formula for keckite is proposed: CaMn(Fe 3+,Mn) 2 Fe 3+ 2(OH) 3(H 2O) 7[PO 4] 4.