Small Serrabrancaite crystals in a vug in vernadite (Specimen size: 4.7 cm) Locality: Alto Serra Branca Pegmatite, near Pedra Lavrada, Paraiba, Brazil — Photo: Thomas Witzke · CC BY-SA 3.0 de
Vernadite
A poorly crystalline hydrous manganese oxide — the amorphous counterpart to birnessite in marine nodules and rock coatings.
Intro adapted from Wikipedia (CC BY-SA).
Vernadite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Mn,Fe,Ca,Na)(O,OH)₂·nH₂O.
Key properties: specific gravity 2.9–3.
IMA symbol Vnd, IMA status: questionable, named in 1944.
A weathering product of other manganese oxides, carbonates, and silicates; easily formed by the action of Fe, Mn-oxidizing bacteria.
It is found associated with Todorokite, pyrolusite, romanèchite, cryptomelane, manganite, ferrihydrite.
The name refers to Professor Vladimir Ivanovich Vernadsky (1863–1945), Russian naturalist and geochemist, Moscow University, Moscow, Russia.