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Bi243+Cr86+O57(OH)6 · 3H2O
Yellow to dirty ...
3 - 4
Named for Duke University, North Carolina and for the Duke Family.
Unique combination of elements. Third natural bismuth-bearing chromate after chrombismite and 'unnamed (Bi chromate oxide)'.

The structure is based on irregular layers of Biφn polyhedra, with φ being O, OH, and H2O; the layers are parallel to (001), linked together by chromate tetrahedra. One of chromate groups shares all vertices with bismuth polyhedra, while the other three chromate groups have only three vertices shared.

Classification of Dukeite


7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
F : With large and medium-sized cations
Dana 7th ed.:

Physical Properties of Dukeite

Diaphaneity (Transparency):
Yellow to dirty yellow-brown
Bright Yellow
Hardness (Mohs):
3 - 4
7.171 g/cm3 (Calculated)

Optical Data of Dukeite

RI values:
nα = 2.330 nβ = 2.370
Max Birefringence:
δ = 2.330
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Very High
Very weak
Colour in reflected light:
Gray to purplish gray
Internal Reflections:
Yellow (strong)

Chemical Properties of Dukeite

Bi243+Cr86+O57(OH)6 · 3H2O
Elements listed in formula:
Analytical Data:
Electron microprobe, wt.%, water content calculated; empirical formula is based on 66 oxygen atoms
Bi2O3 85.06
CrO3 11.65
V2O5 0.59
H2O 1.67

total 98.97
Common Impurities:

Crystallography of Dukeite

Crystal System:
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
P3 1c
Cell Parameters:
a = 15.067(3) Å, c = 15.293(4) Å
a:c = 1 : 1.015
Unit Cell Volume:
V 3007 ų

Type Occurrence of Dukeite

General Appearance of Type Material:
grouped sheaves / acicular crystals, possibly pseudomorphous after unnamed phase; aggregates are 1 x 0.3 mm2, and individuals up to 100 x 1-2 µm
Place of Conservation of Type Material:
Smithsonian Institution, Washington (catalogue number 172012)
Empirical Formula:
Associated Minerals at Type Locality:

Relationship of Dukeite to other Species

7.DF.05UklonskoviteNaMg(SO4)F · 2H2O
7.DF.10KainiteKMg(SO4)Cl · 3H2O
7.DF.15NatrochalciteNaCu2(SO4)2(OH) · 2H2O
7.DF.20MetasideronatriteNa2Fe(SO4)2(OH) · H2O
7.DF.20SideronatriteNa2Fe(SO4)2(OH) · 3H2O
7.DF.25DespujolsiteCa3Mn4+(SO4)2(OH)6 · 3H2O
7.DF.25FleischeritePb3Ge(SO4)2(OH)6 · 3H2O
7.DF.25SchaurteiteCa3Ge(SO4)2(OH)6 · 4H2O
7.DF.25MallestigitePb3Sb5+(SO4)(AsO4)(OH)6 · 3H2O
7.DF.30Slavíkite(H3O+)3Mg6Fe15(SO4)21(OH)18 · 98H2O
7.DF.35MetavoltineNa6K2FeFe6(SO4)12O2 · 18H2O
7.DF.40LannoniteMg2Ca4Al4(SO4)8F8 · 24H2O
7.DF.40VlodavetsiteAlCa2(SO4)2F2Cl · 4H2O
7.DF.45PeretaiteCa(SbO)4(SO4)2(OH)2 · 2H2O
7.DF.50GordaiteNaZn4(SO4)(OH)6Cl · 6H2O
7.DF.55Clairite(NH4)2Fe3(SO4)4(OH)3 · 3H2O
7.DF.60ArzruniteCu4Pb2(SO4)(OH)4Cl6 · 2H2O (?)
7.DF.65ElyitePb4Cu(SO4)O2(OH)4 · H2O
7.DF.70YecoraiteFe33+Bi5(Te6+O4)2(Te4+O3)O9 · 9H2O
7.DF.75RiomarinaiteBi(SO4)(OH) · H2O
7.DF.85XocolatliteCa2Mn24+(Te6+O6)2 · H2O

Other Names for Dukeite

Name in Other Languages:

Other Information

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

References for Dukeite

Reference List:
Burns, P. C., Roberts, A. C., Stirling, J. A. R., Criddle, A. J. and Feinglos, M. N. (2000): Dukeite, Bi243+Cr86+O57(OH)6(H2O)3, a new mineral from Brejauba, Minas Gerais, Brazil: description and crystal structure. American Mineralogist: 85: 1822-1827.

Internet Links for Dukeite URL:
Please feel free to link to this page.

Localities for Dukeite

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.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Brazil (TL)
  • Minas Gerais
    • Conceição do Mato Dentro
      • São José de Brejaúba
[MinRec 32:416]
  • Grand Est
    • Vosges
Georges Favreau
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