Fahleite
A valid IMA mineral species
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About Fahleite
Rolf Fahle
Formula:
CaZn5Fe3+2(AsO4)6 · 14H2O
Colour:
Yellow, grey, bright-green
Lustre:
Silky, Pearly
Hardness:
2
Specific Gravity:
3.08 (Calculated)
Crystal System:
Orthorhombic
Member of:
Name:
Named in honor of Rolf Fahle (1943– ), Munich, Germany, a mineral dealer specializing in Tsumeb minerals, who supplied the type specimen.
Unique Identifiers
Mindat ID:
1436
Long-form identifier:
mindat:1:1:1436:2
Similar Names
| Fahlit | A synonym of 'Tennantite-Tetrahedrite Series' | |
| Faialite | A synonym of Fayalite | |
| Felite | A synonym of Larnite | |
| Vaalite | A variety of Vermiculite | (Mg,Fe)7(Si,Al,Fe)8O20(OH)4 · 2H2O |
| Valaite |
IMA Classification of Fahleite
Approved
IMA Formula:
CaZn2+5Fe3+2(As5+O4)6·14H2O
Approval year:
1982
First published:
1988
Classification of Fahleite
8.CH.55
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
H : With large and medium-sized cations, RO4:H2O < 1:1
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
H : With large and medium-sized cations, RO4:H2O < 1:1
40.5.8.2
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
5 : AXO4·xH2O
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
5 : AXO4·xH2O
20.3.21
20 : Arsenates (also arsenates with phosphate, but without other anions)
3 : Arsenates of Zn, Cd or Hg
20 : Arsenates (also arsenates with phosphate, but without other anions)
3 : Arsenates of Zn, Cd or Hg
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 |
|---|---|---|
| Fhl | 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 Fahleite
Silky, Pearly
Transparency:
Transparent
Colour:
Yellow, grey, bright-green
Hardness:
2 on Mohs scale
Tenacity:
Sectile
Cleavage:
Perfect
⊥ fiber length
⊥ fiber length
Density:
3.08 g/cm3 (Calculated)
Optical Data of Fahleite
Type:
Biaxial (+)
RI values:
nα = 1.628(1) nβ = 1.631(1) nγ = 1.656(1)
2V:
Measured: 39° , Calculated: 40°
Max. Birefringence:
δ = 0.028
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:
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.
Dispersion:
weak to distinct
Chemistry of Fahleite
Mindat Formula:
CaZn5Fe3+2(AsO4)6 · 14H2O
Element Weights:
Crystallography of Fahleite
Crystal System:
Orthorhombic
Cell Parameters:
a = 6.4 Å, b = 11.72 Å, c = 21.9 Å
Ratio:
a:b:c = 0.546 : 1 : 1.869
Unit Cell V:
1,642.68 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals are curved and twisted, in fibrous bundles, to about 1.5 cm;
Comment:
point and space groups not determined
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 22 Å | (100) |
| 11 Å | (100) |
| 3.2 Å | (80) |
| 2.9 Å | (50) |
| 1.65 Å | (20) |
Comments:
Poorly crystalline; only five diffuse lines.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] |
Type Occurrence of Fahleite
General Appearance of Type Material:
Crystals are curved and twisted, in fibrous bundles
Place of Conservation of Type Material:
Mineralogical Institute, Ruhr University, Bochum, Germany.
Geological Setting of Type Material:
Oxidation zone
Associated Minerals at Type Locality:
Synonyms of Fahleite
Other Language Names for Fahleite
Relationship of Fahleite to other Species
Common Associates
Associations Based on Photo Data:
| 2 photos of Fahleite associated with 'Mineral GS1 (of Gebhard)' | Zn, Fe, As, O, H |
| 1 photo of Fahleite associated with Gypsum | CaSO4 · 2H2O |
Related Minerals - Strunz-mindat Grouping
| 8.CH.05 | Natrowalentaite | [Fe3+0.5Na0.5(H2O)6][NaAs3+2(Fe3+2.33W6+0.67)(PO4)2O7] |
| 8.CH.05 | Walentaite | [Mn2+(H2O)6][◻As3+3Fe3+3(PO4)2O7] |
| 8.CH.05 | Halilsarpite | [Mg(H2O)6][CaAs3+2(Fe3+2.67Mo6+0.33)(AsO4)2O7] |
| 8.CH.10 | Anapaite | Ca2Fe2+(PO4)2 · 4H2O |
| 8.CH.15 | Picropharmacolite | Ca4Mg(AsO4)2(HAsO4)2 · 11H2O |
| 8.CH.20 | Dittmarite | (NH4)Mg(PO4) · H2O |
| 8.CH.20 | Niahite | (NH4)Mn2+(PO4) · H2O |
| 8.CH.25 | Taranakite | K3Al5(PO3OH)6(PO4)2 · 18H2O |
| 8.CH.25 | Francoanellite | K3Al5(PO3OH)6(PO4)2 · 12H2O |
| 8.CH.25 | Macivorite | (NH4)3Al5(PO3OH)6(PO4)2 · 18H2O |
| 8.CH.30 | Schertelite | (NH4)2MgH2(PO4)2 · 4H2O |
| 8.CH.35 | Hannayite | (NH4)2Mg3H4(PO4)4 · 8H2O |
| 8.CH.40 | Hazenite | KNaMg2(PO4)2 · 14H2O |
| 8.CH.40 | Struvite-(K) | KMg(PO4) · 6H2O |
| 8.CH.40 | Struvite | (NH4)Mg(PO4) · 6H2O |
| 8.CH.45 | Rimkorolgite | (Mg,Mn)5(Ba,Sr,Ca)(PO4)4 · 8H2O |
| 8.CH.50 | Bakhchisaraitsevite | Na2Mg5(PO4)4 · 7H2O |
| 8.CH.55 | Smolyaninovite | Co3Fe3+2(AsO4)4 · 11H2O |
| 8.CH.60 | Barahonaite-(Fe) | (Ca,Cu,Na,Fe3+,Al)12Fe3+2(AsO4)8(OH,Cl)x · nH2O |
| 8.CH.60 | Barahonaite-(Al) | (Ca,Cu,Na,Fe3+,Al)12Al2(AsO4)8(OH,Cl)x · nH2O |
| 8.CH.70 | Epifanovite | NaCaCu5(PO4)4[AsO2(OH)2] · 7H2O |
| 8.CH.75 | Esdanaite-(Ce) | NaMnCe(PO4)2 · 4H2O |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Fahleite
mindat.org URL:
https://www.mindat.org/min-1436.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Fahleite
Reference List:
Localities for Fahleite
Showing 1 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Namibia (TL) | |
| Medenbach et al. (1988) |
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Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia