Brownish crystals of the very rare cesium mineral hydroxykenomicrolite from one of the few known localities for the mineral (Tanco Mine, Bernic Lake, Lac-du-Bonnet, Manitoba, Canada). Cesium minerals are extremely rare in nature, only about 30 mineral species are known to be Ce containing minerals. Ex Vandenbroucke Museum collection specimen, from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Hydroxykenomicrolite
A vacancy-rich, hydroxyl-bearing member of the microlite group — a hydrated tantalum oxide.
Intro adapted from Wikipedia (CC BY-SA).
Hydroxykenomicrolite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula ( ,Na,Sb³⁺)₂Ta₂O₆(OH).
It crystallizes in the cubic crystal system (space group Fd3m). It is a member of the Pyrochlore-microlite structural group.
Key properties: Mohs hardness 5; specific gravity 6.4–6.6; Adamantine to vitreous luster.
IMA symbol Hykmic, IMA status: approved, named in 1980.
A rare accessory in some highly fractionated granite pegmatites.
It is found associated with Simpsonite, stibiotantalite, microlite, wodginite, tantalite, pollucite, sosedkoite (Kola Peninsula, Russia); kimrobinsonite, manganotantalite.
The name refers to a member of the microlite group with prefixes to indicate dominant OH- (hydroxy) in the Y site and essential vacancies (keno) in the A site. Formerly ‘cesstibtantite’.