Silvery platy crystals of extremely rare Mn-Sb mineral melanostibite with perfect cleavages in matrix from the type and only one of very few known localities for the species (Sjögruvan, Grythyttan, Hällefors, Örebro County, Sweden). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Melanostibite
Melanostibite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Mn²⁺(Sb⁵⁺,Fe³⁺)O₃.
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Corundum structural group.
Key properties: Mohs hardness 4; specific gravity 5.24; Pale rouge-red to cherry-red streak; Brilliant luster.
IMA symbol Mlsb, IMA status: approved, named in 1893.
Found as a very rare mineral in fissures in banded dolomite, in a small Fe–Mn orebody in manganoan dolomite.
It is found associated with Dolomite.
Its name comes from the Greek for black, for its color, and antimony, STIBium, in its composition.