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Lukrahnite

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Tsumeb, Otjikoto (Oshikoto) Region, Namibia
© Marko Burkhardt

Show Lukrahnite Photos (5)
Formula:
Ca(Cu,Zn)(Fe
3+
 
,Zn)[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
System:TriclinicColour:yellow
Lustre:Dull, EarthyHardness:5
Name:For Ludger Krahn (b. 1957), mineral collector of Krefeld, Germany, who provided the initial specimen for study.


Ca analogue of Gartrellite

Classification of Lukrahnite

IMA status:Approved 1999
Strunz 8th edition ID:7/C.31-78
Nickel-Strunz 10th (pending) edition ID:8.CG.20

8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
G : With large and medium-sized cations, RO4:H2O = 1:1
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Type Occurrence of Lukrahnite

Type Locality:Tsumeb Mine (Tsumcorp Mine), Tsumeb, Otjikoto (Oshikoto) Region, Namibia
Associated Minerals at type locality:
WulfeniteQuartzCuprian AdamiteConichalciteChalcocite
Beudantite

Physical Properties of Lukrahnite

Lustre:Dull, Earthy
Diaphaneity (Transparency):Transparent
Colour:yellow
Streak:light yellow
Hardness (Mohs):5
Hardness (Vickers):VHN25=630 kg/mm2
Hardness Data:Measured
Tenacity:Brittle
Cleavage:None Observed
Density (calculated):4.18 g/cm3

Crystallography of Lukrahnite

Crystal System:Triclinic
Class (H-M):1 - Pinacoidal
Space Group:P1
Cell Parameters:a = 5.457Å, b = 5.539Å, c = 7.399Å
α = 68.43°, β = 68.9°, γ = 69.44°
Ratio:a:b:c = 0.985 : 1 : 1.336
Unit Cell Volume:V 187.8 ų
Z:1
Twinning:None mentioned
X-Ray Powder Diffraction:
d-spacingIntensity
4.953 (22)
4.444 (20)
3.416 (100)
3.186 (40)
2.927 (64)
2.832 (26)
2.700 (30)
2.533 (30)

Optical Data of Lukrahnite

Type:Biaxial (+)
RI values: nα = 1.830 nβ = 1.834 nγ = 1.890
2V:Measured: 30°
Maximum Birefringence:δ = 0.060

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High
Pleochroism:Visible
Comments:X=yellow
Y=Z=pale yellow
Orientation could not be determined

Chemical Properties of Lukrahnite

Formula:
Ca(Cu,Zn)(Fe
3+
 
,Zn)[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
Essential elements:As, Ca, Cu, Fe, H, O
All elements listed in formula:As, Ca, Cu, Fe, H, O, Zn
Analytical Data:Average values out of nine sets of electron microprobe data (with H2O calculated to give OH + H2O = 2)
CaO   (11.42%)
NiO   (0.05%)
CoO   (0.15%)
CuO   (10.00%)
ZnO   (8.19%)
PbO   (0.69%)
Al2O3 (0.37%)
Fe2O3 (13.75%)
P2O5  (0.16%)
As2O5 (47.72%)
SO3   (0.09%)
H2O   (6.21%)

Total: 98.80 wt.%
Empirical Formula:
(Ca
 
0.97
Pb
 
0.01
Co
 
0.01
)
 
Σ0.99
(Cu
 
0.60
Zn
 
0.48
)
 
Σ1.08
(Fe
3+
0.82
Al
 
0.03
)
 
Σ0.85
[(AsO
 
4
)
 
1.98
(PO
 
4
)
 
0.01
(SO
 
4
)
 
0.01
]
 
Σ2.00
[(H
 
2
O)
 
1.30
(OH)
 
0.70
]
 
Σ2.00

Relationship of Lukrahnite to other Species

Member of Group:
Tsumcorite Group:
AB(XO
 
4
)
 
2
(OH,H
 
2
O)
 
2
Related Minerals - Nickel-Strunz Grouping):

- +
8.CG.05Cassidyite
Ca
 
2
(Ni
2+
 
,Mg)[PO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Collinsite
Ca
 
2
(Mg,Fe
2+
 
)[PO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Fairfieldite
Ca
 
2
(Mn
2+
 
,Fe
2+
 
)[PO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Gaitite
Ca
 
2
Zn[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Messelite
Ca
 
2
(Fe
2+
 
,Mn
2+
 
)[PO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Parabrandtite
Ca
 
2
Mn
2+
 
[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05Talmessite
Ca
 
2
Mg[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.05β-Uranophane
Ca(UO
 
2
)
 
2
[HSiO
 
4
]
 
2
 · 5H
 
2
O
8.CG.05Hillite
Ca
 
2
(Zn,Mg)[PO
 
4
]
 
2
 · 2 H
 
2
O
8.CG.10Brandtite
Ca
 
2
(Mn
2+
 
,Mg)[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.10Roselite
Ca
 
2
(Co
2+
 
,Mg)[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.10Wendwilsonite
Ca
 
2
(Mg,Co
2+
 
)[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.10Zincroselite
Ca
 
2
Zn[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.15Ferrilotharmeyerite
Ca(Fe
3+
 
,Zn)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Lotharmeyerite
Ca(Zn,Mn
3+
 
)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Mawbyite
Pb(Fe
3+
 
,Zn)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Mounanaite
PbFe
3+
2
[VO
 
4
]
 
2
 · 2(OH,F)
8.CG.15Thometzekite
Pb(Cu,Zn)
 
2
[AsO
 
4
,SO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Tsumcorite
Pb(Zn,Fe
3+
 
)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Cobaltlotharmeyerite
Ca(Co,Fe
3+
 
,Ni)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Cabalzarite
Ca(Mg,Al,Fe
3+
 
)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Krettnichite
(Pb,Sr)(Mn
3+
 
,Co)
 
2
[VO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Cobalttsumcorite
Pb(Co,Fe
3+
 
,Ni)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Nickellotharmeyerite
Ca(Ni,Fe
3+
 
,Co)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.15Manganlotharmeyerite
Ca(Mn
3+
 
,Zn)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Schneebergite
(Bi
3+
 
,Ca)(Co,Ni,Fe
3+
 
)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.15Nickelschneebergite
(Bi
3+
 
,Ca)(Ni,Co,Fe
3+
 
)
 
2
[AsO
 
4
]
 
2
 · 2(OH,H
 
2
O)
8.CG.20Gartrellite
Pb(Cu,Fe
3+
 
,Zn)
 
2
[AsO
 
4
,SO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.20Helmutwinklerite
Pb(Zn,Cu)
 
2
[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.20Zincgartrellite
Pb(Zn,Fe
3+
 
,Cu)
 
2
[AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.20Rappoldite
Pb(Co,Ni,Zn)
 
2
[AsO
 
4
]
 
2
 · 2H
 
2
O
8.CG.20Phosphogartrellite
Pb(Cu,Fe
3+
 
)
 
2
[PO
 
4
,AsO
 
4
]
 
2
 · 2(H
 
2
O,OH)
8.CG.25Pottsite
HPbBi(VO
 
4
)
 
2
·2H
 
2
O
8.CG.35Nickeltalmessite
Ca
 
2
Ni(AsO
 
4
)
 
2
·2H
 
2
O

Other Names for Lukrahnite

Synonyms:
IMA1999-030
Other Languages:
German:Lukrahnit
Spanish:Lukrahnita

Other Information

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

References for Lukrahnite

Reference List:Krause, W., Blass, G., Bernhardt, H.-J. and Effenberger, H. (2001): Lukrahnite, CaCuFe3+(AsO4)2[(H2O)(OH)], the calcium analogue of gartrellite. Neues Jahrbuch für Mineralogie, Monatshefte (2001): 481-492.

Internet Links for Lukrahnite

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    Localities for Lukrahnite

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