About the nomenclature: manganate or manganite?
Let's go down the ladder.  $\ce{KMnO4}$ is permanganate, Mn(VII).  $\ce{K2MnO4}$ is manganate, Mn(VI).  $\ce{K4MnO4}$ is manganite, Mn(IV).  $\ce{LaMnO3}$ is called both manganate and manganite, but Mn(III). In a proper world it should be lower than that manganite.  They are pedagogically both wrong if it is La(III).

http://dictionary.sensagent.com/potassium%20manganite/en-en/

Manganese oxidation state nomenclature is a real world mess. Drawing nomenclature parallels to Cl(VII) and downward is not valid.  Drawing nomenclature parallels to titanium is poor, for Ti(IV) is the highest common oxidation state.  $\ce{SrO + TiO2}$ gives $\ce{SrTiO3}$, properly called titanate, for it is Ti(IV) on both sides.

Organic had the same problem. The highest valence carbocation was tricoordinate, hence a carbonium ion.  Magic Acid gave $\ce{CH5^+}$.  Carbonium ions were renamed carbenium ions to general confusion.  Then, $\ce{CH6^{2+}}$.  Organic dropped the ball with direction of optical rotation versus geometric left and right.  It was flat out stupid designating E ("trans") and Z ("cis") olefins.  The designation should have been abstract rather than language-originated.