Tantalite-(Fe) Locality: Linópolis, Divino das Laranjeiras , Doce valley, Minas Gerais , Southeast Region, Brazil ( Locality at mindat.org ) Size: 5.8 x 4.9 x 2.8 cm. This is a heavy (163 grams), sharp crystal with stunning lustre and unusually equant form. The thin striations that run laterally along the large faces give it depth and dimensionality, though it is overall a thin crystal relative to its width in front. It is complete on the top and right/upper terminations and complete on most of the downward pointing left termination as well. The small flower of crystallized albite is a contrast in the center is a fine accent. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Tantalite-(Fe)
The mineral group tantalite [(Fe, Mn)Ta2O6] is the primary source of the chemical element tantalum, a corrosion (heat and acid) resistant metal. It is chemically similar to columbite, and the two are often grouped together as a semi-singular mineral called coltan or "columbite-tantalite" in many mineral guides. However, tantalite has a much greater specific gravity than columbite (8.0+ compared to columbite's 5.2). Iron-rich tantalite is the mineral tantalite-(Fe) or ferrotantalite and manganese-rich is tantalite-(Mn) or manganotantalite. Tantalite is also very close to tapiolite.
Intro adapted from Wikipedia (CC BY-SA).
Tantalite-(Fe) is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Fe²⁺Ta₂O₆.
It crystallizes in the orthorhombic crystal system. It is a member of the Columbite structural group.
Key properties: Mohs hardness 6–6.5; specific gravity 6.65–7.95; Black streak; Submetallic to vitreous luster; optically biaxial.
IMA symbol Ttl-Fe, IMA status: approved, named in 1836.
Occurs as an accessory and primary constituent of granite pegmatites.
It is found associated with Tapiolite-(Fe).
Suffix for dominant Fe in the composition and relation to tantalite-(Mg) and tantalite-(Mn), named for the Greek mythical Tantalus, for the difficulty in bringing the mineral into solution.