Ranciéite-Takanelite Series, Calcite

Ball of Takanelite on calcite crystals. This unusual manganese oxide is found on an upper level of the oxidised zone of the deposit on calcite veins.


The "Takanelite" was analyzed and verified By Ralph Bottrill from Mineral Resources Tasmania. Specimen and Photograph Andrew Tuma.

Ralph Bottrill's comments via email on Analysis -

"I analysed this by XRD and it gave a pattern very close to that for
takanelite, with a significant admixture of an asbolane-type mineral.
I checked it with semiquantitative SEM/EDAX and it gave mostly Mn with
only a small amount of Ca, fitting takanelite. It could find no Ni or
Co, so the "asbolane" remains unproven.
Interestingly, although there is meant to be a series from takanelite
to ranceite, the data in Mindat indicates some significant differences
in chemical formulae, unit cell and powder pattern - may need looking
at?"

However after more detailed research by Jeff Post from the Smithsonian showed that indeed the mineral is closer to Rancieite that could grade into Takanelite. So early investigation by R. Bottrill from the initial find is likely takanelite while the second find as tested from an adjacent area of the deposit is Rancieite.

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