Found on a museum specimen labeled from the San Jose mine, Brejauba, Minas Gerais, Brazil. Corrected locality is Lavra da Posse, Sao Jose de Berjauba, Conceicao do Mato Dentro County, Link to MinDat.org Location Data.
Name Origin:
Named for Duke University, Duham, North Carolina, USA and for the Mary Duke Biddle Foundation.
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Burns P C , Roberts A C , Stirling J A R , Criddle A J , Feinglos M N , American Mineralogist , 85 (2000) p.1822-1827, Dukeite, Bi24Cr8O57(OH)6(H2O)3, a new mineral from Brejauba, Minas Gerais,, Brazil: Description and crystal structure
Physical Properties of Dukeite
Cleavage:
None
Color:
Yellow, Dirty yellow brown.
Diaphaneity:
Translucent to transparent
Fracture:
Brittle - Uneven - Very brittle fracture producing uneven fragments.
Habit:
Acicular - Occurs as needle-like crystals.
Habit:
Wheat Sheaf - Bundle shaped aggregates resembling wheat sheafs after hand reaping wheat.
Hardness:
3-4 - Calcite-Fluorite
Luster:
Resinous
Streak:
bright yellow
Optical Properties of Dukeite
Gladstone-Dale:
CI calc= -0.053 (Good) - where the CI = (1-KPDcalc/KC) KPDcalc= 0.188,KC= 0.1785 Ncalc = 2.28
Optical Data:
Uniaxial (?), a=2.33, b=2.37, bire=0.0400.
RL Bireflectance:
Very weak.
RL Color:
Gray to purplish-gray with strong yellow internal reflections aligned with crystal direction.
RL Pleochroism:
Mid orange-brown.
Reflectivity
Standardized Intensity (100%) Reflection Spectra of Dukeite in Air
λ
R1
R2
∑ R1(λ)
∑ R2(λ)
400 nm
19.80
21.40
420 nm
19.45
20.85
440 nm
18.90
20.05
460 nm
18.15
19.00
470 nm
17.90
18.60
480 nm
17.50
18.20
500 nm
17.00
17.55
520 nm
16.70
17.30
540 nm
16.50
17.10
546 nm
16.45
17.00
560 nm
16.30
16.90
580 nm
16.20
16.70
589 nm
16.00
16.50
600 nm
15.95
16.45
620 nm
15.80
16.25
640 nm
15.70
16.20
650 nm
15.70
16.20
660 nm
15.60
16.10
680 nm
15.50
15.95
700 nm
15.35
15.80
Standardized Intensity (100%) Reflection Spectra of Dukeite in Oil
λ
R1
R2
∑ R1(λ)
∑ R2(λ)
400 nm
7.60
9.01
420 nm
7.34
8.43
440 nm
6.80
7.61
460 nm
6.34
6.94
470 nm
6.11
6.65
480 nm
5.85
6.41
500 nm
5.48
5.98
520 nm
5.47
5.92
540 nm
5.46
5.95
546 nm
5.43
5.94
560 nm
5.32
5.88
580 nm
5.27
5.82
589 nm
5.19
5.67
600 nm
5.20
5.64
620 nm
5.12
5.64
640 nm
5.06
5.58
650 nm
5.00
5.57
660 nm
5.01
5.56
680 nm
4.95
5.56
700 nm
4.90
5.58
Calculated Relative Intensity Colors of Dukeite in Air
Relative Intensity
0%
60%
100%
120%
180%
240%
300%
360%
420%
480%
540%
550%
R1
R2
Calculated Relative Intensity Colors of Dukeite in Oil
Relative Intensity
0%
100%
200%
300%
400%
500%
600%
700%
800%
900%
1000%
R1
R2
Calculated Properties of Dukeite
Electron Density:
Bulk Density (Electron Density)=6.02 gm/cc note: Specific Gravity of Dukeite =7.18 gm/cc.
Fermion Index:
Fermion Index = 0.0061589959 Boson Index = 0.9938410041
Photoelectric:
PEDukeite =1,483.23 barns/electron U=PEDukeite x rElectron Density=8,926.62 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Dukeite is Not Radioactive