Multiple oxide, tapiolite group, tantalum-bearing mineral, forms a series with the much less common tapiolite-(Mn)
Specific gravity: 7.90
Hardness: 6 to 6½
Streak: Brownish black
Tapiolite-(Fe) occurs as an accessory mineral in zoned granite
pegmatites, and is detrital in placers. Associated minerals include
triplite and triphylite
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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