Tantalite

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).[3] Iron-rich tantalite is the mineral tantalite-(Fe) or ferrotantalite and manganese-rich is tantalite-(Mn) or manganotantalite.

Not to be confused with Tantalit or Tantalate.
Tantalite
Tantalite, Pilbara district, Australia
General
CategoryOxide minerals
Formula
(repeating unit)		(Fe,Mn)Ta2O6
IMA symbolTtl[1]
Strunz classification4.DB.35
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPbcn (no. 60)
Identification
ColorDark black, iron-black to dark brown, reddish brown
CleavageGood in one direction
FractureSubconchoidal
Mohs scale hardness6-6.5
LusterSubmetallic to almost resinous
StreakBrownish-red to black
Specific gravity8.0+
References[2][3]

Tantalite is also very close to tapiolite. Those minerals have the same chemical composition, but different crystal symmetry: orthorhombic for tantalite and tetragonal for tapiolite.[4]

Tantalite is black to brown in both color and streak. Manganese-rich tantalites can be brown and translucent.

Occurrence
Manganotantalite from Alto do Giz, RN, Brazil

Tantalite occurs in granitic pegmatites that are rich in rare-elements, and in placer deposits derived from such rocks.[5] It has been found in Australia, Brazil, Canada, Colombia (Guainía and Vichada), Egypt, northern Europe, Madagascar, Namibia, Nigeria, Rwanda, The Democratic Republic of Congo, the United States (California, Colorado, Maine, and Virginia), and Zimbabwe. Brazil has the world's largest reserve of tantalite (52.1%).[6]

Applications

The tantalum metal extracted from tantalite is used in alloys for strength and higher melting points, in glass to increase the index of refraction, and in surgical steel, as it is non-reactive and non-irritating to body tissues. Much like glass, it is not suitable for use in hydrofluoric acid and strong hot alkali applications.[7]

Sustainability

The mining of tantalite causes many environmental and social problems in the Democratic Republic of Congo.[8][9]

See also

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. "TANTALITE (Iron Manganese Tantalum Niobium Oxide)". Galleries.com. Retrieved 2011-10-25.
  3. Tantalite. Mindat.org (2011-09-07). Retrieved on 2011-10-30.
  4. P. Cerny; et al. (1992). "The tantalite-tapiolite gap: natural assemblages versus experimental data" (PDF). Canadian Mineralogist. 30: 587.
  5. Melcher, Frank; et al. (June 2008). "Fingerprinting of conflict minerals: columbite-tantalite ("coltan") ores". SGA News (23): 1. Retrieved 10 August 2016.
  6. Papp, John F. (2006). "2006 Minerals Yearbook Nb & Ta". US Geological Survey. Retrieved 2008-06-03.
  7. Titan Metal Fabricators. Alloys. Applications of Tantalum. Retrieved on 2022-07-08.
  8. Coltan, Gorillas and cellphones Archived 2005-04-07 at the Wayback Machine. Cellular-news.com (2001-04-03). Retrieved on 2011-10-30.
  9. The Coltan Scandal. Geology.about.com (2010-07-04). Retrieved on 2011-10-30.
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