Oxystibiomicrolite
An antimony-oxygen member of the microlite group — a rare isometric tantalum oxide.
Intro adapted from Wikipedia (CC BY-SA).
Oxystibiomicrolite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Sb³⁺,Ca)₂Ta₂O₆O.
It crystallizes in the cubic crystal system (space group Fd3m). It is a member of the Pyrochlore-microlite structural group.
Key properties: Mohs hardness 5.5; White streak.
IMA symbol Osmic, IMA status: approved, named in 1938.
A very rare mineral, replacing stibiotantalite, in the lithium-rich albite unit of a complex granite pegmatite (Varuträsk pegmatite, Sweden).
It is found associated with Stibiotantalite, antimony, allemontite, lithiophilite, alkalic beryl, cassiterite, columbite-tantalite, microlite (Varuträsk pegmatite, Sweden).
The name refers to a member of the microlite group with prefixes to indicate essential oxygen (oxy) in the Y site and essential Sb3+ (stibio) in the A site. Formerly ‘stibiomicrolite’.