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Rankamaite

A valid IMA mineral species
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07048570017271926063551.jpg
Rankamaite

Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
04779620017271926096247.jpg
Rankamaite, etc.

Urubu mine, Monte Belo, Itinga, Minas Gerais, Brazil
06127590017271926142217.jpg
Rankamaite

Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
07048570017271926063551.jpg
Rankamaite

Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
04779620017271926096247.jpg
Rankamaite, etc.

Urubu mine, Monte Belo, Itinga, Minas Gerais, Brazil
06127590017271926142217.jpg
Rankamaite

Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
02034110017271926181410.jpg
Rankamaite

Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
04779620017271926096247.jpg
Rankamaite, etc.

Urubu mine, Monte Belo, Itinga, Minas Gerais, Brazil
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About RankamaiteHide

02982970017271926216857.jpg
Professor Kalervo Rankama
Formula:
(Na,K)3(Ta,Nb,Al)11(O,OH)31
Colour:
Creamy-white
Hardness:
3 - 4
Specific Gravity:
5.5
Crystal System:
Orthorhombic
Name:
Named after Professor Kalervo Rankama (22 February 1913 Helsinki – 10 March 1995 Helsinki), geochemist, University of Helsinki, Helsinki, Finland. He made major contributions to the geochemistry of tantalum and niobium.
This page provides mineralogical data about Rankamaite.


Unique IdentifiersHide

Mindat ID:
3362
Long-form identifier:
mindat:1:1:3362:2

IMA Classification of RankamaiteHide

Classification of RankamaiteHide

Strunz-mindat (2025):
4.DM.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
M : With large (+- medium-sized) cations; unclassified
Dana 8th ed.:
8.7.6.1

8 : MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM
7 : Miscellaneous
Hey's CIM Ref.:
18.1.7

18 : Niobates and Tantalates
1 : Niobates and tantalates containing neither rare earths nor U

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference
RkmIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of RankamaiteHide

Colour:
Creamy-white
Comment:
In thin sections, appears bluish-grey to brownish.
Hardness:
3 - 4 on Mohs scale
Density:
5.5 g/cm3 (Measured)    5.84 g/cm3 (Calculated)

Optical Data of RankamaiteHide

Type:
Biaxial
Dispersion:
r < v extreme
Optical Extinction:
Z = c and, X ⊥ c
Comments:
Elongation positive.
Refractive indices > 2.10.

Chemistry of RankamaiteHide

Mindat Formula:
(Na,K)3(Ta,Nb,Al)11(O,OH)31
Element Weights:
Element% weight
Ta77.892 %
O19.409 %
Na2.699 %

Calculated from ideal end-member formula.
Elements listed:
Al, H, K, Na, Nb, O, Ta - search for minerals with similar chemistry

Crystallography of RankamaiteHide

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cmmm
Setting:
Cmmm
Cell Parameters:
a = 17.224(3) Å, b = 17.687(3) Å, c = 3.9361(7) Å
α = 90°, β = 90°, γ = 90°
Ratio:
a:b:c = 0.974 : 1 : 0.223
Unit Cell V:
1199.1 ų
Z:
2
Comment:
Atencio et al. (2011)

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
2.972 Å(100)
3.931 Å(80)
3.010 Å(79)
3.463 Å(47)
3.378 Å(47)
2.787 Å(38)
4.110 Å(33)
4.420 Å(30)
3.189 Å(30)
2.946 Å(30)
Comments:
Atencio et al. (2011)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Near-surface Processes
22 : Hydration and low-? subsurface aqueous alteration (see also #23)
26 : Hadean detrital minerals

Type Occurrence of RankamaiteHide

Type Locality:
ⓘ Mumba cassiterite gravels, Mumba, Osso, Masisi Territory, North Kivu, DR Congo
General Appearance of Type Material:
Water-worn pebbles found in heavy mineral concentrates. Silky, fibrous (asbestiform). The fibers are generally wavy but tufts of straight fibres can be seen in small cavities.
Place of Conservation of Type Material:
n.d.
Geological Setting of Type Material:
Alluvial, probably from a lithium pegmatite. Thought to be an alteration of simpsonite.
Associated Minerals at Type Locality:
CassiteriteMuscoviteSimpsoniteTantalite-(Mn)
Reference:
von Knorring, O., Vorma, A., Nixon, P.H. (1969) Rankamaite, a new tantalum mineral from Kivu, Congo. Bulletin of the Geological Society of Finland, 41. 47-56 doi:10.17741/bgsf/41.003

Synonyms of RankamaiteHide

Other Language Names for RankamaiteHide

German:Rankamait
Spanish:Rankamaita

Common AssociatesHide

Associated Minerals Based on Photo Data:
14 photos of Rankamaite associated with CassiteriteSnO2
7 photos of Rankamaite associated with ThoreauliteSn2+Ta2O6
7 photos of Rankamaite associated with QuartzSiO2
4 photos of Rankamaite associated with LithiotantiteLiTa3O8
4 photos of Rankamaite associated with AlbiteNa(AlSi3O8)
4 photos of Rankamaite associated with SimpsoniteAl4Ta3O13(OH)
2 photos of Rankamaite associated with Tantalite-(Mn)Mn2+Ta2O6
1 photo of Rankamaite associated with WodginiteMn2+Sn4+Ta2O8
1 photo of Rankamaite associated with TourmalineAD3G6(T6O18)(BO3)3X3Z

Related Minerals - Strunz-mindat GroupingHide

4.DM.SugarwhiteitePb2Te5O12Mon. 2/m : P21/b
4.DM.BahariyaiteKMnO4Orth. mmm (2/m 2/m 2/m) : Pnma
4.DM.05Sosedkoite(K,Na)5Al2(Ta,Nb)22O60Orth.
4.DM.15Cesplumtantite(Cs,Na)2(Pb,Sb3+)3Ta8O24Tet.
4.DM.20EyseliteFe3+Ge4+3O7(OH)Orth.
4.DM.25KuranakhitePbMn4+Te6+O6Orth.
4.DM.30MambertiiteBiMo5+2.80O8(OH)Tric. 1 : P1
4.DM.30GelosaiteBiMo6+(2-5x)Mo5+6xO7(OH) · H2O Mon. 2/m : P21/m
4.DM.35EkebergiteThFeNb2O8Mon. 2/m : P2/b
4.DM.45RiesiteTiO2Mon. 2/m : P2/b
4.DM.50SardignaiteBiMo2O7(OH) · 2H2OMon. 2/m : P21/m
4.DM.55Tewite(K1.5◻0.5)(Te1.25W0.25◻0.5)W5O19Orth. mmm (2/m 2/m 2/m) : Pban
4.DM.60WumuiteK(W2.67Al0.33)O9Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm
4.DM.60KingsgateiteZrMo6+2O7(OH)2 · 2H2OTet. 4mm : I41cd
4.DM.60MorningstariteNa(W2.67Fe3+0.33)O9 · H2OHex. 6/mmm (6/m 2/m 2/m) : P6/mmm

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Internet Links for RankamaiteHide

References for RankamaiteHide

Localities for RankamaiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Brazil
 
  • Minas Gerais
    • Itinga
      • Monte Belo
Atencio et al. (2011)
DR Congo (TL)
 
  • North Kivu
    • Masisi Territory
      • Osso
        • Mumba
Safiannikoff et al. (1961) +2 other references
  • Tanganyika
Voloshin A.V. (1988)
Kazakhstan
 
  • East Kazakhstan Region
    • Irtysh River
A.V. Voloshin analytical data
    • Ulan District
Voloshin et al. (1983) +1 other reference
Quick NavTopAbout RankamaiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
 
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