Kidwellite
A valid IMA mineral species
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About Kidwellite
Albert Lewis Kidwell
Formula:
NaFe3+9+x(PO4)6(OH)11 · 3H2O, x = 0.33
Formula is slightly simplified; for details see Kolitsch (2004).
Colour:
Greenish yellow, Greenish white, Yellow, Light green
Lustre:
Resinous, Waxy, Silky, Dull
Hardness:
3
Specific Gravity:
3.04 - 3.3
Crystal System:
Monoclinic
Name:
Named by Paul (Paulus) B. Moore and Jum Ito in 1978 in honor of Albert Lewis (or Laws) Kidwell (1 January 1919, Auxvasse, Missouri, USA - 16 August 2008, Scottsdale, Arizona, USA), mineral collector and research geologist with Carter Oil Company and later Exxon Oil Company, Houston, Texas, USA.
Occurs as replacement of rockbridgeite and beraunite.
Dufrénite or natrodufrénite may overgrow, epitaxially, kidwellite, and vice versa.
May be confused with meurigite-Na.
Dufrénite or natrodufrénite may overgrow, epitaxially, kidwellite, and vice versa.
May be confused with meurigite-Na.
Unique Identifiers
Mindat ID:
2202
Long-form identifier:
mindat:1:1:2202:2
IMA Classification of Kidwellite
Classification of Kidwellite
8.DK.20
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
K : With large and medium-sized cations, (OH, etc.):RO4 > 1:1 and < 2:1
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
K : With large and medium-sized cations, (OH, etc.):RO4 > 1:1 and < 2:1
Dana 7th ed.:
42.8.2.1
42.8.2.1
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
8 : (AB)5(XO4)3Zq·xH2O
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
8 : (AB)5(XO4)3Zq·xH2O
19.14.2
19 : Phosphates
14 : Phosphates of Fe and other metals
19 : Phosphates
14 : Phosphates of Fe and other metals
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 |
|---|---|---|
| Kdw | 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 Kidwellite
Resinous, Waxy, Silky, Dull
Comment:
Frequently matte botryoids with a fine velvety surface
Colour:
Greenish yellow, Greenish white, Yellow, Light green
Streak:
Yellow
Hardness:
3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {100}
Perfect on {100}
Fracture:
Splintery
Density:
3.04 - 3.3 g/cm3 (Measured) 3.34 g/cm3 (Calculated)
Optical Data of Kidwellite
Type:
Biaxial (-)
RI values:
nα = 1.787 nβ = 1.800 nγ = 1.805
Birefringence:
0.018
Max. Birefringence:
δ = 0.018
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.
No measured or calculated 2V is on file for this mineral, so the value used here (63°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (63°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
extreme
Pleochroism:
Non-pleochroic
Chemistry of Kidwellite
Mindat Formula:
NaFe3+9+x(PO4)6(OH)11 · 3H2O, x = 0.33
Formula is slightly simplified; for details see Kolitsch (2004).
Formula is slightly simplified; for details see Kolitsch (2004).
Crystallography of Kidwellite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/b
Setting:
P2/c
Cell Parameters:
a = 20.117 Å, b = 5.185 Å, c = 13.978 Å
β = 107.07°
β = 107.07°
Ratio:
a:b:c = 3.88 : 1 : 2.696
Unit Cell V:
1,393.77 ų (Calculated from Unit Cell)
Morphology:
Usually acicular, but may rarely form almost rod-like crystals.
Comment:
Single-crystal data; slightly As-bearing.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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Perspective On | Perspective Off
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View
CIF File Best | x | y | z | a | b | c
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Rotation
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0014570 | Kidwellite | Kolitsch U (2004) The crystal structures of kidwellite and 'laubmannite', two complex fibrous iron phosphates Mineralogical Magazine 68 147-165 |  | 2004 | Clara mine, Black Forest, Germany | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.41 Å | (100) |
| 6.43 Å | (30) |
| 4.017 Å | (35) |
| 3.813 Å | (40) |
| 3.413 Å | (55) |
| 3.193 Å | (40) |
| 3.173 Å | (35) |
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] |
Geological Setting:
Rarely in phosphate-rich granite pegmatites
Type Occurrence of Kidwellite
General Appearance of Type Material:
Olive green botryoids or bands within other phosphate mineral botryoids.
Geological Setting of Type Material:
Phosphate-bearing iron deposits
Associated Minerals at Type Locality:
Synonyms of Kidwellite
Other Language Names for Kidwellite
Common Associates
Associations Based on Photo Data:
| 217 photos of Kidwellite associated with Strengite | FePO4 · 2H2O |
| 119 photos of Kidwellite associated with Beraunite | Fe3+6(PO4)4O(OH)4 · 6H2O |
| 98 photos of Kidwellite associated with Dufrénite | Ca0.5Fe2+Fe3+5(PO4)4(OH)6 · 2H2O |
| 75 photos of Kidwellite associated with Rockbridgeite | (Fe2+0.5Fe3+0.5)2Fe3+3(PO4)3(OH)5 |
| 53 photos of Kidwellite associated with Cacoxenite | Fe3+24AlO6(PO4)17(OH)12 · 75H2O |
| 42 photos of Kidwellite associated with Goethite | Fe3+O(OH) |
| 22 photos of Kidwellite associated with Leucophosphite | KFe3+2(PO4)2(OH) · 2H2O |
| 22 photos of Kidwellite associated with Natrodufrénite | NaFe3+Fe3+5(PO4)4O(OH)5(H2O)2 |
| 19 photos of Kidwellite associated with Cyrilovite | NaFe3+3(PO4)2(OH)4 · 2H2O |
| 19 photos of Kidwellite associated with Quartz | SiO2 |
Related Minerals - Strunz-mindat Grouping
| 8.DK. | Regerite | KFe6(PO4)4(OH)7(H2O)6 · 4H2O |
| 8.DK. | Richelsdorfite | Ca2Cu5Sb(AsO4)4(OH)6Cl · 6H2O |
| 8.DK. | Bimbowrieite | NaMgFe3+5(PO4)4(OH)6 · 2H2O |
| 8.DK. | Puttapaite | Pb2Mn2+2ZnCr3+4O2(AsO4)4(OH)6 · 12H2O |
| 8.DK.10 | Thalliumpharmacosiderite | TlFe3+4[(AsO4)3(OH)4] · 4H2O |
| 8.DK.10 | Natropharmacosiderite | NaFe3+4(AsO4)3(OH)4 · 4H2O |
| 8.DK.10 | Pharmacosiderite | KFe3+4(AsO4)3(OH)4 · 6-7H2O |
| 8.DK.10 | Plumbopharmacosiderite | Pb0.5Fe3+4(AsO4)3(OH)4 · 5H2O |
| 8.DK.10 | Strontiopharmacosiderite | Sr0.5Fe3+4[(AsO4)3(OH)4] · 4H2O |
| 8.DK.10 | Bariopharmacosiderite | Ba0.5Fe3+4(AsO4)3(OH)4 · 5H2O |
| 8.DK.10 | Hydroniumpharmacosiderite | (H3O)Fe3+4(AsO4)3(OH)4 · 4H2O |
| 8.DK.12 | Hydroniumpharmacoalumite | (H3O)Al4(AsO4)3(OH)4 · 4.5H2O |
| 8.DK.12 | Bariopharmacoalumite | Ba0.5Al4(AsO4)3(OH)4 · 4H2O |
| 8.DK.12 | Pharmacoalumite | KAl4(AsO4)3(OH)4 · 6.5H2O |
| 8.DK.12 | Calciopharmacoalumite | Ca0.5Al4(AsO4)3(OH)4 · 5H2O |
| 8.DK.12 | Natropharmacoalumite | NaAl4(AsO4)3(OH)4 · 4H2O |
| 8.DK.15 | Matioliite | NaMgAl5(PO4)4(OH)6 · 2H2O |
| 8.DK.15 | Burangaite | NaFe2+Al5(PO4)4(OH)6 · 2H2O |
| 8.DK.15 | Natrodufrénite | NaFe3+Fe3+5(PO4)4O(OH)5(H2O)2 |
| 8.DK.15 | Dufrénite | Ca0.5Fe2+Fe3+5(PO4)4(OH)6 · 2H2O |
| 8.DK.15 | Gayite | NaMn2+Fe3+5(PO4)4(OH)6 · 2H2O |
| 8.DK.25 | Bleasdaleite | (Ca,Fe3+)2Cu5(Bi,Cu)(PO4)4(H2O,OH,Cl)13 |
| 8.DK.30 | Matulaite | (Fe3+,Al)Al7(PO4)4(PO3OH)2(OH)8(H2O)8 · 8H2O |
| 8.DK.35 | Krasnovite | Ba(Al,Mg)(PO4,CO3)(OH)2 · H2O |
Fluorescence of Kidwellite
Not fluorescent in UV
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 Kidwellite
mindat.org URL:
https://www.mindat.org/min-2202.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Kidwellite
Reference List:
Moore, Paul B., Ito, Jun (1978) Kidwellite, NaFe93+(OH)10(PO4)6·5H2O, a new species. Mineralogical Magazine, 42 (321) 137-140 doi:10.1180/minmag.1978.042.321.21
Braithwaite, R. S. W., Corke, Hilary (1980) Kidwellite from Cornwall. Mineralogical Magazine, 43 (331) 952-953 doi:10.1180/minmag.1980.043.331.25
Kolitsch, U. (2004) The crystal structures of kidwellite and ‘laubmannite’, two complex fibrous iron phosphates. Mineralogical Magazine, 68 (1) 147-165 doi:10.1180/0026461046810177
Localities for Kidwellite
Showing 70 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.
Australia | |
| Steve Sorrell Collection |
| Birch et al. (1997) |
| Brian Beyer via John Toma (IDs at SA Museum?) +1 other reference |
| Pilkington et al. (1979) +2 other references |
| Birch et al. (1993) +1 other reference |
| Birch et al. (1993) |
Brazil | |
| Sergio Varvello collection |
| Cassedanne et al. (1999) |
Czech Republic | |
| Janouš (1995) +4 other references |
| Vrtiška et al. (2017) |
France | |
| Queneau (n.d.) +1 other reference |
| Chollet Pascal Collection |
| Pierre Le Roch & Jean-Marc Johannet ... |
| Walenta et al. (1980) +1 other reference | |
| Queneau (n.d.) |
Germany | |
| Walenta (1992) +2 other references |
| Habel (2006) |
| Neschen (n.d.) |
| Eddy Vervloet collection |
| Dill (2015) |
| www.mineralienatlas.de (n.d.) |
| Weiß (1990) |
| taunusmineralien.de (2013) |
| Blaß (2002) |
| Stieglitz et al. (1987) +1 other reference |
| Weiß (1990) |
| Hucko (2010) |
| Weiß (1990) |
| Belendorff (2012) |
| Witzke et al. (1997) |
Japan | |
| Matsubara et al. (1980) |
Mali | |
| Gineste (2012) |
Morocco | |
| Favreau (2012) |
Namibia | |
| von Bezing (2007) |
| Keller (1985) | |
| Keller et al. (1989) |
Portugal | |
| Robert Rothenberg Collection 16831-8 |
| Alves (n.d.) |
| Alves (n.d.) | |
| Georges Favreau info +1 other reference |
| desescaut.jy@voila.fr | |
Spain | |
| Sainz de Baranda Graf (2026) |
| Sáinz de Baranda et al. (2004) |
| www.foro-minerales.com (2022) +1 other reference | |
| Calvo et al. (2011) |
Sweden | |
| Bjällerud (1989) +1 other reference |
UK | |
| Mineralogical Magazine +1 other reference |
USA | |
| King et al. (1995) |
| Henry Barwood |
| Rocks & Min.: 64:203. +2 other references | |
| Cook et al. (1982) | |
| Dean (1995) | |
| Mineralogical Magazine 1978 42 : ... +1 other reference |
| Rocks & Min.: 63: 113. +2 other references |
| Smith (1988) |
| Rocks & Min.:64:297-298. |
| Smith (1988) | |
| Smith (1988) |
| Jason Smith & M.E. Ciriotti (2005) |
| SEM/EDS analyzed by Lloyd W. Alexander ... +1 other reference |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Dr. William S. Wise presentation to ... |
| Castor et al. (2004) | |
| PXRD and EDS via Inna Lykova. Found by ... |
| Roberts et al. (1986) |
| Campbell et al. (1985) |
| Dietrich (1990) |
| Watson (1907) +1 other reference |
| Rocks & Min.: 57:20 & 60:168. |
Quick NavTopAbout KidwelliteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatFluorescence Other InformationInternet Links References Localities Locality List
Ste Barbe vein, Montmins mining district, Échassières, Vichy, Allier, Auvergne-Rhône-Alpes, France