Cadwaladerite
A valid IMA mineral species - grandfathered
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About Cadwaladerite
Charles M. B. Cadwalader
Formula:
Al5(H2O)3(OH)12 · n(Cl,H2O)
Colour:
Yellow
Lustre:
Vitreous
Specific Gravity:
1.66
Crystal System:
Isometric
Name:
Named in honor of Charles Meigs Biddle Cadwalader (3 June 1885, Fort Washington, Pennsylvania, USA - 18 June 1959, Whitemarsh, Pennsylvania, USA), Managing Director and President of the Academy of Natural Sciences, Philadelphia, Pennsylvania, USA, between 1928 and 1951.
Type Locality:
It was demonstrated that cadwaladerite and lesukite are the same mineral species. Because cadwaladerite has historical precedence, it is recognized as a valid mineral species, whereas lesukite is discredited (IMA proposal 18-H), see Peterson et al. (2019).
When the mineral is washed, Cl is lost from the crystal structure and the refractive index decreases (Peterson et al., 2019)
When the mineral is washed, Cl is lost from the crystal structure and the refractive index decreases (Peterson et al., 2019)
Unique Identifiers
Mindat ID:
845
Long-form identifier:
mindat:1:1:845:1
IMA Classification of Cadwaladerite
Approved, 'Grandfathered' (first described prior to 1959)
IMA status notes:
Redefined by the IMA
IMA Formula:
Al2(OH)5Cl·2H2O
First published:
1941
Approval history:
2019: Redefined by IMA Al5(H2O)3(OH)12·n(Cl,H2O) (IMA proposal 18-H).
Classification of Cadwaladerite
3.BD.05
3 : HALIDES
B : Simple halides, with H2O
D : Simple halides with H2O and additional OH
3 : HALIDES
B : Simple halides, with H2O
D : Simple halides with H2O and additional OH
10.5.1.1
10 : OXYHALIDES AND HYDROXYHALIDES
5 : Am(O,OH)pXq
10 : OXYHALIDES AND HYDROXYHALIDES
5 : Am(O,OH)pXq
8.6.3
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
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 |
|---|---|---|
| Cwd | 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 Cadwaladerite
Vitreous
Transparency:
Transparent
Colour:
Yellow
Fracture:
Conchoidal
Density:
1.66 g/cm3 (Measured)
Optical Data of Cadwaladerite
Type:
Isotropic
RI values:
nα = 1.511 - 1.563
Birefringence:
Isotropic minerals have no birefringence
Surface Relief:
Moderate
Comments:
Refractive index depends on Cl content (washing decreases Cl content).
Chemistry of Cadwaladerite
Mindat Formula:
Al5(H2O)3(OH)12 · n(Cl,H2O)
Element Weights:
Elements listed:
Crystallography of Cadwaladerite
Crystal System:
Isometric
Class (H-M):
23 - Tetartoidal
Space Group:
I213
Cell Parameters:
a = 19.840(12) Å
Unit Cell V:
7,809.53 ų (Calculated from Unit Cell)
Morphology:
Amorphous grains and small masses. Tiny cubic crystals.
Comment:
Formerly assumed to be amorphous. Space group and unit cell from Peterson et al. (2019). Range of unit-cell parameter a: 19.788 to 19.859 Å.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.76 Å | (80) |
| 8.1 Å | (100) |
| 7.03 Å | (60) |
| 5.33 Å | (20) |
| 5.01 Å | (20) |
| 4.43 Å | (50) |
| 4.08 Å | (20) |
| 2.69 Å | (80) |
| 2.44 Å | (50) |
| 2.33 Å | (20) |
| 2.21 Å | (20) |
Comments:
Type material #134143 (Peterson et al. 2019).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] |
Geological Setting:
Evaporitic, coal fires, fumaroles.
Type Occurrence of Cadwaladerite
General Appearance of Type Material:
Grains and small masses in halite.
Place of Conservation of Type Material:
Harvard University, Cambridge, Massachusetts,, USA, number 134143.
Geological Setting of Type Material:
Complex of small sulfate outcrops, at the edge of an evaporite basin.
Associated Minerals at Type Locality:
Synonyms of Cadwaladerite
Other Language Names for Cadwaladerite
Common Associates
Associations Based on Photo Data:
| 2 photos of Cadwaladerite associated with Jarosite | KFe3+3(SO4)2(OH)6 |
| 1 photo of Cadwaladerite associated with Tondiite | Cu3Mg(OH)6Cl2 |
| 1 photo of Cadwaladerite associated with Hydrokenoralstonite | Na0.5(Al,Mg)2(F,OH)6 · H2O |
| 1 photo of Cadwaladerite associated with Anhydrite | CaSO4 |
| 1 photo of Cadwaladerite associated with Native Sulphur | S8 |
Related Minerals - Strunz-mindat Grouping
| 3.BD.15 | Korshunovskite | Mg2Cl(OH)3 · 4H2O |
| 3.BD.20 | Nepskoeite | Mg4Cl(OH)7 · 6H2O |
| 3.BD.25 | Koenenite | Na4Mg9Al4Cl12(OH)22 |
Other Information
Notes:
Weakly hygroscopic.
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 Cadwaladerite
mindat.org URL:
https://www.mindat.org/min-845.html
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References for Cadwaladerite
Reference List:
Witzke, T. (1997) A new aluminium chloride mineral from Oelsnitz near Zwickau, Saxony, Germany. Neues Jahrbuch für Mineralogie - Monatshefte, 1997 (7) 301-308 doi:10.1127/njmm/1997/1997/301
Miyawaki, Ritsuro, Hatert, Frédéric, Pasero, Marco, Mills, Stuart J. (2019) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 49. European Journal of Mineralogy, 31 (3) 653-658 doi:10.1127/ejm/2019/0031-2861
Peterson, Ronald C., Metcalf, Mallory, Kampf, Anthony R., Contreira Filho, Reynaldo R., Reid, Joel, Joy, Brian (2019) Cadwaladerite, Al2(H2O)(OH)4·n(Cl,OH–,H2O), from Cerros Pintados, Chile, defined as a valid mineral species and the discreditation of lesukite. The Canadian Mineralogist, 57 (6) 827-841 doi:10.3749/canmin.1900040
Localities for Cadwaladerite
Showing 12 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.
Chile | |
| Natural History Museum Vienna collection (obtained from Udo Hörig, PXRD-analysed by Uwe Kolitsch) |
| SEM-EDS by Igor V. Pekov |
| In the collection of Brent Thorne. ... +1 other reference |
| Notulae Naturae et al. (1941) +2 other references |
Czech Republic | |
| Hyrsl J. +3 other references |
DR Congo | |
| Mbo et al. (2023) |
Germany | |
| Witzke (1997) |
Iran | |
| Vincent Bourgoin |
Kyrgyzstan | |
| Museum of Victoria specimen no: M 46880 |
Poland | |
| Kruszewski (2012) |
Russia | |
| Vergasova et al. (1997) |
Spain | |
| Rewitzer et al. (2018) |
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Maria Mine, Caleta Vítor mining district, Arica Province, Arica y Parinacota, Chile