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Dukeite

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Formula:
Bi243+Cr86+O57(OH)6 · 3H2O
System:
Trigonal
Colour:
Yellow to dirty ...
Lustre:
Resinous
Hardness:
3 - 4
Name:
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

Approved
7.DF.80

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.:
35.4.6.1

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)
Associated Minerals at Type Locality:

Physical Properties of Dukeite

Resinous
Diaphaneity (Transparency):
Transparent
Colour:
Yellow to dirty yellow-brown
Streak:
Bright Yellow
Hardness (Mohs):
3 - 4
Tenacity:
Brittle
Density:
7.171 g/cm3 (Calculated)

Crystallography of Dukeite

Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
P3 1c
Cell Parameters:
a = 15.067(3) Å, c = 15.293(4) Å
Ratio:
a:c = 1 : 1.015
Unit Cell Volume:
V 3007 ų
Z:
2

Optical Data of Dukeite

Type:
Uniaxial
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
Bireflectance:
Very weak
Colour in reflected light:
Gray to purplish gray
Internal Reflections:
Yellow (strong)

Chemical Properties of Dukeite

Formula:
Bi243+Cr86+O57(OH)6 · 3H2O
All 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
Empirical Formula:
Bi3+23.95(Cr6+7.64V5+0.43)Σ8.07O56.84(OH)6.16⋅3.01H2O
Common Impurities:
V

Relationship of Dukeite to other Species

7.DF.05UklonskoviteNaMg(SO4)(OH) · 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:
German:Dukeit
Russian:Дюкит
Spanish:Dukeita

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

mindat.org URL:
http://www.mindat.org/min-7089.html
Please feel free to link to this page.

Localities for Dukeite

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 (São José de Bryamba)
[MinRec 32:416]
France
 
  • Lorraine
    • Vosges
Georges Favreau
Mineral and/or Locality  
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