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Lukrahnite
A valid IMA mineral species
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About Lukrahnite
Dr. Ludger Krahn
Formula:
CaCuFe3+(AsO4)2(OH,H2O)2
Colour:
yellow
Lustre:
Dull, Earthy
Hardness:
5
Specific Gravity:
4.18 (Calculated)
Crystal System:
Triclinic
Member of:
Name:
For Ludger Krahn (b. 1957), mineral collector of Krefeld, Germany, who provided the initial specimen for study.
Unique Identifiers
Mindat ID:
11010
Long-form identifier:
mindat:1:1:11010:9
IMA Classification of Lukrahnite
Classification of Lukrahnite
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
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
G : With large and medium-sized cations, RO4:H2O = 1:1
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Lkr | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Lukrahnite
Dull, Earthy
Transparency:
Transparent
Colour:
Yellow
Streak:
Light yellow
Hardness:
5 on Mohs scale
Hardness:
VHN25=630 kg/mm2 - Vickers
Hardness Data:
Measured
Tenacity:
Brittle
Cleavage:
None Observed
Density:
4.18 g/cm3 (Calculated)
Optical Data of Lukrahnite
Type:
Biaxial (+)
RI values:
nα = 1.83 nβ = 1.834 nγ = 1.89
2V:
Measured: 30°
Max. Birefringence:
δ = 0.060
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Pleochroism:
Visible
Comments:
X=yellow
Y=Z=pale yellow
Orientation could not be determined
Y=Z=pale yellow
Orientation could not be determined
Chemistry of Lukrahnite
Mindat Formula:
CaCuFe3+(AsO4)2(OH,H2O)2
Element Weights:
Crystallography of Lukrahnite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 5.457 Å, b = 5.539 Å, c = 7.399 Å
α = 68.43°, β = 68.9°, γ = 69.44°
α = 68.43°, β = 68.9°, γ = 69.44°
Ratio:
a:b:c = 0.985 : 1 : 1.336
Unit Cell V:
187.8 ų
Z:
1
Twinning:
None mentioned
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.953 Å | (22) |
| 4.444 Å | (20) |
| 3.416 Å | (100) |
| 3.186 Å | (40) |
| 2.927 Å | (64) |
| 2.832 Å | (26) |
| 2.700 Å | (30) |
| 2.533 Å | (30) |
| 2.468 Å | (25) |
Comments:
Tsumeb, Namibia. Data from the type description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] |
Type Occurrence of Lukrahnite
General Appearance of Type Material:
Spherical aggregates up to 0.5 mm; individual grains < 30 microns.
Place of Conservation of Type Material:
Mineralogical Institute, University of Bochum, Germany.
Associated Minerals at Type Locality:
Synonyms of Lukrahnite
Other Language Names for Lukrahnite
Relationship of Lukrahnite to other Species
Member of:
Other Members of Tsumcorite Group:
| Alumolukrahnite | Ca[CuAl](AsO4)2(H2O,OH)2 | Tric. 1 : P1 |
| Cabalzarite | CaMg2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Cobaltlotharmeyerite | CaCo2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Cobalttsumcorite | PbCo2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Ferrilotharmeyerite | CaZnFe3+(AsO4)2(OH) · H2O | Mon. 2/m : B2/m |
| Gartrellite | PbCuFe3+(AsO4)2(OH) · H2O | Tric. 1 : P1 |
| Helmutwinklerite | PbZn2(AsO4)2 · 2H2O | Tric. 1 : P1 |
| Kaliochalcite | KCu2(SO4)2[(OH)(H2O)] | Mon. 2/m : B2/m |
| Krettnichite | PbMn3+2(VO4)2(OH)2 | Mon. 2/m : B2/m |
| Lotharmeyerite | CaZn2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Manganlotharmeyerite | CaMn3+2(AsO4)2(OH)2 | Mon. 2/m : B2/m |
| Mawbyite | PbFe3+2(AsO4)2(OH)2 | Mon. 2/m : B2/m |
| Mounanaite | PbFe3+2(VO4)2(OH)2 | Mon. 2/m : B2/m |
| Natrochalcite | NaCu2(SO4)2(OH) · 2H2O | Mon. 2/m : B2/m |
| Nickellotharmeyerite | CaNi2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Nickelschneebergite | BiNi2(AsO4)2(OH) · H2O | Mon. 2/m : B2/m |
| Nickeltsumcorite | Pb(Ni,Fe3+)2(AsO4)2(H2O,OH)2 | Mon. 2/m : B2/m |
| Phosphogartrellite | PbCuFe3+(PO4)2(OH,H2O)2 | Tric. 1 : P1 |
| Rappoldite | PbCo2(AsO4)2 · 2H2O | Tric. 1 : P1 |
| Schneebergite | BiCo2(AsO4)2(OH) · H2O | Mon. 2/m : B2/m |
| Thometzekite | PbCu2+2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Tsumcorite | PbZn2(AsO4)2 · 2H2O | Mon. 2/m : B2/m |
| Yancowinnaite | PbCuAl(AsO4)2OH · H2O | Tric. 1 : P1 |
| Zincgartrellite | PbZn2(AsO4)2(H2O,OH)2 | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
| 14 photos of Lukrahnite associated with Olivenite | Cu2(AsO4)(OH) |
| 6 photos of Lukrahnite associated with Quartz | SiO2 |
| 6 photos of Lukrahnite associated with Beudantite | PbFe3+3(AsO4)(SO4)(OH)6 |
| 2 photos of Lukrahnite associated with Conichalcite | CaCu(AsO4)(OH) |
| 2 photos of Lukrahnite associated with Cuprite | Cu2O |
| 1 photo of Lukrahnite associated with Mimetite | Pb5(AsO4)3Cl |
| 1 photo of Lukrahnite associated with Wulfenite | Pb(MoO4) |
Related Minerals - Strunz-mindat Grouping
| 8.CG. | Fluckite | CaMn2+(AsO3OH)2 · 2H2O |
| 8.CG. | Dondoellite | Ca2Fe(PO4)2 · 2H2O |
| 8.CG. | 'Ca-Huréaulite' | CaMn5(PO4)4 · 4H2O |
| 8.CG. | Alumolukrahnite | Ca[CuAl](AsO4)2(H2O,OH)2 |
| 8.CG.05 | Parabrandtite | Ca2Mn2+(AsO4)2 · 2H2O |
| 8.CG.05 | Talmessite | Ca2Mg(AsO4)2 · 2H2O |
| 8.CG.05 | Collinsite | Ca2Mg(PO4)2 · 2H2O |
| 8.CG.05 | Messelite | Ca2Fe2+(PO4)2 · 2H2O |
| 8.CG.05 | Gaitite | Ca2Zn(AsO4)2 · 2H2O |
| 8.CG.05 | Anorthoroselite | Ca2Co(AsO4)2 · 2H2O |
| 8.CG.05 | Cassidyite | Ca2Ni(PO4)2 · 2H2O |
| 8.CG.05 | Fairfieldite | Ca2Mn2+(PO4)2 · 2H2O |
| 8.CG.05 | Hillite | Ca2Zn(PO4)2 · 2H2O |
| 8.CG.05 | 'Unnamed (Fe2+-analogue of Parabrandtite)' | Ca2Fe2+(AsO4)2 · 2H2O |
| 8.CG.10 | Zincroselite | Ca2Zn(AsO4)2 · 2H2O |
| 8.CG.10 | Roselite | Ca2Co(AsO4)2 · 2H2O |
| 8.CG.10 | Rruffite | Ca2Cu(AsO4)2 · 2H2O |
| 8.CG.10 | Wendwilsonite | Ca2Mg(AsO4)2 · 2H2O |
| 8.CG.10 | Brandtite | Ca2Mn2+(AsO4)2 · 2H2O |
| 8.CG.10 | 'Unnamed (Fe2+-analogue of Brandtite)' | Ca2Fe2+(AsO4)2 · 2H2O |
| 8.CG.15 | Mawbyite | PbFe3+2(AsO4)2(OH)2 |
| 8.CG.15 | Thometzekite | PbCu2+2(AsO4)2 · 2H2O |
| 8.CG.15 | Yancowinnaite | PbCuAl(AsO4)2OH · H2O |
| 8.CG.15 | Schneebergite | BiCo2(AsO4)2(OH) · H2O |
| 8.CG.15 | Cabalzarite | CaMg2(AsO4)2 · 2H2O |
| 8.CG.15 | Nickelschneebergite | BiNi2(AsO4)2(OH) · H2O |
| 8.CG.15 | Lotharmeyerite | CaZn2(AsO4)2 · 2H2O |
| 8.CG.15 | Nickeltsumcorite | Pb(Ni,Fe3+)2(AsO4)2(H2O,OH)2 |
| 8.CG.15 | Magnesiofluckite | CaMg(AsO3OH)2(H2O)2 |
| 8.CG.15 | Krettnichite | PbMn3+2(VO4)2(OH)2 |
| 8.CG.15 | Cobalttsumcorite | PbCo2(AsO4)2 · 2H2O |
| 8.CG.15 | Manganlotharmeyerite | CaMn3+2(AsO4)2(OH)2 |
| 8.CG.15 | Tsumcorite | PbZn2(AsO4)2 · 2H2O |
| 8.CG.15 | Ferrilotharmeyerite | CaZnFe3+(AsO4)2(OH) · H2O |
| 8.CG.15 | Cobaltlotharmeyerite | CaCo2(AsO4)2 · 2H2O |
| 8.CG.15 | Mounanaite | PbFe3+2(VO4)2(OH)2 |
| 8.CG.15 | Nickellotharmeyerite | CaNi2(AsO4)2 · 2H2O |
| 8.CG.20 | Helmutwinklerite | PbZn2(AsO4)2 · 2H2O |
| 8.CG.20 | Phosphogartrellite | PbCuFe3+(PO4)2(OH,H2O)2 |
| 8.CG.20 | Gartrellite | PbCuFe3+(AsO4)2(OH) · H2O |
| 8.CG.20 | Zincgartrellite | PbZn2(AsO4)2(H2O,OH)2 |
| 8.CG.20 |
Clara Mine, Oberwolfach, Ortenaukreis, Freiburg Region, Baden-Württemberg, Germany