Olive green microcrystals of the extremely rare mineral gravegliaite grown on a big perfect alabandite crystal, from the classic locality of Merelani (Merelani Hills, Arusha Region, Tanzania (United Republic)). Analyzed specimen. — Photo: David Hospital · CC BY-SA 4.0
Gravegliaite
Gravegliaite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Mn²⁺(S⁴⁺O₃)·3H₂O.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Gravegliaite structural group.
Key properties: specific gravity 2.39; White streak; Vitreous luster; optically biaxial.
IMA symbol Gvg, IMA status: approved, named in 1990.
Very rare, along fractures in metamorphosed manganiferous layers in radiolarian cherts in an ophiolite sequence.
It is found associated with Tephroite, bementite, braunite, hausmannite, hematite.
The name refers to Val Graveglia, Italy, within which the Gambatesa mine is located.