Miguelromeroite formula ?

Hello,

Does the formula, MnMn2Mn2(AsO4)2(HAsO4)2 · 4H2O, mean that the Manganese occupies three distinctly different locations?

Steven


To absent friends...in memory...still bright.

Steve, you are probably correct, and it also suggests that some hureaulite, having the same structure, containing large amounts of Fe or Ca, could be different species based on site occupancy.

Yes, it does.

Before Miguelromeroite was defined as a distinct species, it was considered as Villyaellenite. And the formula of Villyaellenite was written Mn5(AsO4)2(HAsO4) · 4H2O or (Mn,Ca)5(AsO4)2(HAsO4) · 4H2O (which is essentially the same).

When the two species were split, Villyaellenite was redefined as Ca-dominant in one position, while Mn remained dominant in two positioned, i.e. an ordered intermediate member of the series between Sainfeldite and Miguelromeroite.

The formula of Miguelromeroite was thus written as MnMn2Mn2(AsO4)2(HAsO4)2 · 4H2O to reflect the structural similarity, as well as the difference from the formula of Villyaellenite.

Lefteris.