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Formula: Fe2+Ta2O6
Multiple oxide, tapiolite group, tantalum-bearing
mineral, forms a series with the much less common tapiolite-(Mn)
Crystal System: Tetragonal
Specific gravity: 7.90 measured, 8.17 calculated
Hardness: 6 to 6½
Streak: Brownish black
Colour: Black
Environments
Tapiolite-(Fe) occurs as an accessory mineral in zoned granite
pegmatites, and is detrital in placers. Associated minerals include
albite, muscovite,
tourmaline, beryl,
spodumene,
columbite–tantalite,
wodginite, cassiterite,
triplite and triphylite
(HOM).
Localities
At the La Viquita pegmatite, Sierra de la Estanzuela, Chacabuco Department,
San Luis Province, Argentina, the paragenesis in the spodumene-bearing
granitic pegmatite evolved
from the border zone inward.
Early phases consist of minor columbite-(Fe) in the border and
wall zones.
In the intermediate zones, with inwardly increasing proportions of spodumene,
columbite-(Fe) crystals occur in the outer parts, and locally rare
columbite-(Mn).
In the middle and inner intermediate zones, the dominant phases are cassiterite,
wodginite with elevated zirconium content and
ferrowodginite. All members of the wodginite
group carry some signs of exsolution-induced lamellae of tapiolite-(Fe). Tapiolite-(Fe) is dominant in small units of the
core-margin association, with intergrowths of ferrotitanowodginite, inclusions of
hafnium-bearing zircon, and late-stage cassiterite
(CM 46.379-393).
At the Tanco Mine, Bernic Lake, Lac-du-Bonnet area, Manitoba, Canada, tapiolite-(Fe) occurs with
wodginite, tantalite,
ixiolite and microlite
(Dana).
At the Odd West pegmatite, Rush Lake, Lac-du-Bonnet area, Manitoba, Canada,
pegmatite penetrates a metamorphosed
graywacke, bordered by granodioritic
to granitic plutons. The pegmatite
is rich in lithium, rubidium, cesium,
tantalum and tin. The margins of the
pegmatite consist predominantly of albite
and quartz, with subordinate quartz and
microcline-perthite. Grain sizes increase
gradually towards the centre of the body, which consists mainly of blocky
microcline-perthite and
quartz, with subordinate amounts of montebrasite
and spodumene, and minor lithium
mica. In a zone intermediate between the hanging-wall margins and the core,
cassiterite up to 5 cm and brownish-black to dark green
tourmaline are relatively abundant in a coarse-grained
albite-quartz matrix. Tapiolite-(Fe),
stibiotantalite and antimony-bearing
microlite occur in this assemblage as rare grains, up to 2 cm long. Tapiolite-(Fe)
forms rounded to subhedral grains embedded in stibiotantalite
(CM 12.76-78).
At the Suzhou granitic complex, Anhui, China, in the upper part of the
granite, three facies are distinguished; from the top down, these are (l) an
albite-dominant facies, (2) a topaz-bearing facies, and
(3) a biotite-bearing facies. Columbite-(Fe)
occurs in the biotite-bearing facies, and
columbite-(Fe) to columbite-(Mn) is
found in the topaz-bearing facies. Tantalite-(Fe)
and tapiolite-(Fe) are concentrated in the albite-dominant facies. The tapiolite-(Fe)
is restricted to the albite-dominant facies and is associated with grains of
tantalite, hafnium-bearing zircon and
thorite
(CM 35.699-706).
The type ocality is Kulmala, Sukula Pegmatites, Tammela, Tavastia Proper, Finland.
Near Otorokua Point, southern Westland, South Island, New Zealand, rare particles of tapiolite-(Fe) in were found in beach sands,
by panning black sand. Associated minerals included garnet,
monazite,
clinozoisite-epidote,
tourmaline, allanite and
titanite
(AM 43.112–119).
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