Yellow microcrystals of the extremely rare mineral omsite (IMA 2012-025) associated to minoritary ullmanite from the type and only one of two known localities worldwide: Correc d'en Llinassos, Oms, Pyrénées-Orientales, Occitanie, France. — Photo: David Hospital · CC BY-SA 4.0
Omsite
Omsite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ni₂Fe³⁺(OH)₆[Sb(OH)₆].
It crystallizes in the hexagonal crystal system (space group P-3). It is a member of the Hydrotalcite structural group.
Key properties: Mohs hardness 3; specific gravity 3.378; Pale yellow streak; Vitreous to resinous luster; optically uniaxial.
IMA symbol Om, IMA status: approved, named in 2012.
Found in narrow, crystal-lined fractures cutting massive siderite-bearing rock.
It is found associated with Ullmannite, chalcopyrite, tetrahedrite/tennantite, siderite, glaukosphaerite.
The name refers to Oms, a village close to the locality that produced the first specimens.