Gengenbachite
A valid IMA mineral species
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Formula:
KFe3+3(PO3OH)4[PO2(OH)2]2 · 6H2O
Colour:
Pale brown
Lustre:
Vitreous
Hardness:
2
Specific Gravity:
2.4
Crystal System:
Trigonal
Name:
For the town of Gengenbach, adjacent to the type locality.
This page provides mineralogical data about Gengenbachite.
Unique Identifiers
Mindat ID:
29254
Long-form identifier:
mindat:1:1:29254:6
GUID
(UUID V4):
(UUID V4):
d6bd3335-5d0b-4944-8757-fca90db270da
IMA Classification of Gengenbachite
Classification of Gengenbachite
8.CA.65
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
A : With small and large/medium cations
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
A : With small and large/medium cations
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 |
---|---|---|
Gnb | 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 Gengenbachite
Vitreous
Transparency:
Translucent
Colour:
Pale brown
Streak:
White
Hardness:
2 on Mohs scale
Hardness Data:
Estimated
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Irregular/Uneven
Density:
2.4(5) g/cm3 (Measured) 2.43(2) g/cm3 (Calculated)
Optical Data of Gengenbachite
Type:
Uniaxial (+)
RI values:
nω = 1.592(2) nε = 1.596(2)
Max Birefringence:
δ = 0.004
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Optical Extinction:
Anomalous pale brownish interference colours.
Chemistry of Gengenbachite
Mindat Formula:
KFe3+3(PO3OH)4[PO2(OH)2]2 · 6H2O
Crystallography of Gengenbachite
Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
P3 1c
Cell Parameters:
a = 9.12(1) Å, c = 16.84(2) Å
Ratio:
a:c = 1 : 1.846
Unit Cell V:
1,213.00 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Simple hexagonal prisms.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
---|---|---|---|---|---|---|---|
0020142 | Gengenbachite | Hu Z B, Wang C X, Tong C Q, Huang Y X, Pan Y, Mi J X (2013) Crystal structure and magnetic property of synthetic gengenbachite, KH8(Fe2.66Al0.34)(PO4)6*6H2O The Canadian Mineralogist 51 223-232 | 2013 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
d-spacing | Intensity |
---|---|
7.89 Å | (4) |
7.16 Å | (10) |
4.57 Å | (7) |
3.57 Å | (5) |
3.23 Å | (6) |
3.09 Å | (8) |
2.87 Å | (4) |
2.81 Å | (5) |
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] |
Type Occurrence of Gengenbachite
General Appearance of Type Material:
Hexagonal columnar crystals intergrown with haigerachite. The reach a maximum of about 0.06 mm in length.
Place of Conservation of Type Material:
n.d.
Associated Minerals at Type Locality:
Synonyms of Gengenbachite
Other Language Names for Gengenbachite
German:Gengenbachit
Related Minerals - Strunz-mindat Grouping
8.CA. | Davidlloydite | Zn3(AsO4)2 · 4H2O |
8.CA. | Apexite | NaMg(PO4) · 9H2O |
8.CA. | Brandãoite | BeAl2(PO4)2(OH)2(H2O)5 |
8.CA.05 | Fransoletite | Ca3Be2(PO4)2(PO3OH)2 · 4H2O |
8.CA.05 | Parafransoletite | Ca3Be2(PO4)2(PO3OH)2 · 4H2O |
8.CA.10 | Ehrleite | Ca4Be3Zn2(PO4)6 · 9H2O |
8.CA.15 | Faheyite | Be2Mn2+Fe3+2(PO4)4 · 6H2O |
8.CA.20 | Gainesite | Na(Na,K)(Be,Li)Zr2(PO4)4 · 1.5-2H2O |
8.CA.20 | Mccrillisite | NaCs(Be,Li)Zr2(PO4)4 · 1-2H2O |
8.CA.20 | Selwynite | NaK(Be,Al)Zr2(PO4)4 · 2H2O |
8.CA.25 | Pahasapaite | Li8(Ca,Li,K)10.5Be24(PO4)24 · 38H2O |
8.CA.30 | Hopeite | ZnZn2(PO4)2 · 4H2O |
8.CA.30 | Arsenohopeite | Zn3(AsO4)2 · 4H2O |
8.CA.30 | Nizamoffite | Mn2+Zn2(PO4)2(H2O)4 |
8.CA.30 | Unnamed (Mg-analogue of Hopeite) | Mg3(PO4)2 · 4H2O |
8.CA.35 | Warikahnite | Zn3(AsO4)2 · 2H2O |
8.CA.40 | Phosphophyllite | Zn2Fe(PO4)2 · 4H2O |
8.CA.42 | Steinmetzite | Zn2Fe3+(PO4)2(OH) · 3H2O |
8.CA.45 | Parascholzite | CaZn2(PO4)2 · 2H2O |
8.CA.45 | Scholzite | CaZn2(PO4)2 · 2H2O |
8.CA.50 | Keyite | Cu2+3Zn4Cd2(AsO4)6 · 2H2O |
8.CA.55 | Pushcharovskite | K0.6Cu18[AsO2(OH)2]4[AsO3OH]10(AsO4)(OH)9.6 · 18.6H2O |
8.CA.60 | Prosperite | Ca2Zn4(AsO4)4 · H2O |
8.CA.70 | Parahopeite | Zn3(PO4)2 · 4H2O |
8.CA.70 | Reaphookhillite | MgZn2(PO4)2 · 4H2O |
8.CA.75 | Stergiouite | CaZn2(AsO4)2 · 4H2O |
8.CA.80 | Limousinite | BaCa[Be4P4O16] · 6H2O |
8.CA.85 | Minjiangite | BaBe2(PO4)2 |
8.CA.85 | Wilancookite | (Ba5Li2◻)Ba6Be24P24O96 · 26H2O |
Other Information
Notes:
Soluble in dilute 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.
Internet Links for Gengenbachite
mindat.org URL:
https://www.mindat.org/min-29254.html
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References for Gengenbachite
Reference List:
Localities for Gengenbachite
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).
Struck out - Mineral was erroneously reported from this locality.
Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.
All localities listed without proper references should be considered as questionable.
Germany (TL) | |
| Walenta K. & Theye (2004) |
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Gengenbach, Ortenaukreis, Freiburg Region, Baden-Württemberg, Germany