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Formula: Mn2+TiTa2O8
Oxide, wodginite group,
columbite supergroup,
manganese-, titanium- and
tantalum- bearing mineral
Crystal System: Monoclinic
Specific gravity: 6.86 measured, 6.89 calculated
Hardness: 5½
Streak: Dark brown
Colour: Dark brown to black
Luminescence: Not fluorescent under UV
Common impurities: Fe,Sn,Sc,Nb
Environments
Localities
At the type locality, the Tanco Mine, Bernic Lake, Lac-du-Bonnet area, Manitoba, Canada,
titanium is largely a ubiquitous component in
wodginite group minerals; however,
titanium contents are typically low. The first
titanium-rich variety of
wodginite encountered was the type
ferrowodginite sample; subsequently a re-examination of the
tantalum- and niobium-
oxide minerals at Tanco led to the discovery of titanowodginite, with TiO2 contents as high as
10.4wt %.
Type titanowodginite occurs in a sample of tantalum ore from the
workings of the Tanco pegmatite. The mineral occurs with
microlite and
columbite-(Mn) as disseminations in a silicate matrix consisting
of saccharoidal albite plus quartz
with minor muscovite and beryl.
Type titanowodginite occurs as euhedral, bipyramidal crystals ranging from a few mm to 1 cm long. It occurs
most often in irregular clusters of crystals, but it also occurs as individual crystals.
(CM 30.633-638).
At the Separation Rapids Lithium Project (Separation Lake area), Kenora District, Ontario, Canada,
wodginite, ferrowodginite
and titanowodginite have been discovered in rare-element
granitic
pegmatites which occur in the Separation Rapids
pegmatite field. The
pegmatites intrude a metavolcanic
(greenstone) belt, where they are associated with a
rare-element-enriched granitic intrusion, the Separation Rapids
pluton.
At Separation Rapids, the rare-metal oxides follow two distinct evolutionary paths:
(i) columbite-(Fe) →
columbite-(Fe) +
ferrowodginite →
ferrotantalite +
ferrowodginite →
microlite group minerals
(ii) columbite-(Mn) →
columbite-(Mn) +
wodginite →
tantalite-(Mn) +
wodginite →
microlite group minerals
(CM 36.2.637–658).
At Fonte del Prete, San Piero in Campo, Campo nell'Elba, Livorno Province, Tuscany, Italy, the rare-element-enriched
granitic
pegmatite dike displays
LCT(lithium - cesium -
tantalum)-type geochemical features. The dike is characterised by complex
asymmetrical zoning, with miarolitic pockets containing primitive or highly evolved assemblages. There is a
noteworthy presence of niobium and
tantalum oxides and complex oxides, occurring mainly in the pockets.
Euxenite-(Y),
polycrase-(Y), uranium- and
bismuth- rich polycrase-(Y),
and columbite-(Fe) occur in the primitive pockets in the central
part (core zone), whereas uranium- and
bismuth- rich polycrase-(Y),
uranopolycrase,
columbite-(Mn),
tantalite-(Mn),
wolframoixiolite, titanowodginite and
microlite are found in the evolved pockets, at the extremities of the
dike.
Niobium-bearing rutile and
euxenite-(Y) are also found in the massive
pegmatite.
During the evolution of the pegmatite, a volatile-rich
melt with a high content of rare elements reached saturation in aqueous vapour. Minerals of
titanium, niobium,
iron, yttrium + heavy rare-earth
elements occur in the primitive pockets; the enrichment of manganese,
tantalum and tungsten in the
evolved ones led to the crystallisation of minerals with high Ta/(Ta + Nb) and Mn/(Mn + Fe) values, such as
tantalite-(Mn),
microlite and titanowodginite. The
polycrase-(Y) is unusually enriched in
bismuth and uranium, and is zoned
from a bismuth-poor core to a
bismuth-rich rim.
(CM 40.3.799–814).
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