A single brown aggregate of the very rare tantalum oxide hydroxide mineral hydrokenomicrolite-3R but labeled as the discredited name parabariomicrolite from the type locality of the mineral in Brasil: Alto do Giz Pegmatite, Equador, Borborema Province, Rio Grande do Norte, Brazil. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Hydrokenomicrolite
Hydrokenomicrolite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula ( ,H₂O)₂Ta₂(O,OH)₆(H₂O).
It crystallizes in the cubic crystal system (space group Fd3m). It is a member of the Pyrochlore-microlite structural group.
Key properties: Mohs hardness 4.5–5; specific gravity 6.666; White streak; Adamantine to resinous luster.
IMA symbol Hkmic, IMA status: approved, named in 2011.
An accessory mineral in the heavy mineral concentrate from a zoned granitic pegmatite.
It is found associated with Microcline, albite, quartz, muscovite, spodumene, “lepidolite”, cassiterite, tantalite-(Mn), monazite-(Ce), fluorite, “apatite”, beryl, “garnet”, epidote.
The name refers to a member of the microlite subgroup with the A site dominated by vacancies, the B site by Ta, and the Y site by H2O.