Log In
Cuatrocapaite-(K)
A valid IMA mineral species
This page is currently not sponsored. Click here to sponsor this page.
About Cuatrocapaite-(K)
Formula:
K3(NaMg◻)(As2O3)6Cl6 · 16H2O
Colour:
Colorless
Lustre:
Vitreous
Hardness:
2½
Specific Gravity:
2.76
Crystal System:
Trigonal
Member of:
Name:
Cuatrocapaite-(K) is named in allusion to the structure, which consists of four (cuatro in Spanish) different types of layers (capa in Spanish): (1) [K, (NH4)], (2)[(Na,Mg,□)3(H2O)16], (3)[As2O3] and (4) [Cl6]. The -(K) suffix indicates the dominant cation in the large-cation layer. The IPA pronunciation of cuatrocapaite is (/kwa: troʊ 'ka: pa: aɪt/).
The K analogue of cuatrocapaite-(NH4) (IMA No. 2018-083).
There are 4 types of layers in the structure:
- a planar, neutral As2O3 (arsenite) one,
- an (NH4+,K+) layer standing for a link for the adjacent arsenite sheets,
- a Cl– one, located on the As sides of the arsenite layers,
- a layer with partially occupied Na, Mg, and H2O sites, flanked on both its sides by the Cl- layers.
The layer sequence of the first three types layers is identical that observed in lucabindiite and gajardoite.
There are 4 types of layers in the structure:
- a planar, neutral As2O3 (arsenite) one,
- an (NH4+,K+) layer standing for a link for the adjacent arsenite sheets,
- a Cl– one, located on the As sides of the arsenite layers,
- a layer with partially occupied Na, Mg, and H2O sites, flanked on both its sides by the Cl- layers.
The layer sequence of the first three types layers is identical that observed in lucabindiite and gajardoite.
Unique Identifiers
Mindat ID:
53211
Long-form identifier:
mindat:1:1:53211:6
Similar Names
| Cuatrocapaite-(NH4) | A valid IMA mineral species | (NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2O |
IMA Classification of Cuatrocapaite-(K)
Approved
IMA Formula:
K3(NaMg◻)(As3+2O3)6Cl6·16H2O
Approval year:
2018
First published:
2019
Type description reference:
Kampf, Anthony R., Chukanov, Nikita V., Möhn, Gerhard, Dini, Maurizio, Molina Donoso, Arturo A., Friis, Henrik (2019) Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite. Mineralogical Magazine, 83 (5) 741-748 doi:10.1180/mgm.2019.26
Classification of Cuatrocapaite-(K)
3.DC.
3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
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 |
|---|---|---|
| Ctc-K | 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 Cuatrocapaite-(K)
Vitreous
Transparency:
Transparent
Colour:
Colorless
Streak:
White
Hardness:
2½ on Mohs scale
Comment:
ca.
Tenacity:
Flexible
Cleavage:
Perfect
Perfect on {001}
Perfect on {001}
Fracture:
Irregular/Uneven
Comment:
not elastic
Density:
2.76(2) g/cm3 (Measured) 2.771 g/cm3 (Calculated)
Optical Data of Cuatrocapaite-(K)
Type:
Uniaxial (-)
RI values:
nω = 1.777(3) nε = 1.539(3)
Max. Birefringence:
δ = 0.238
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 uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Pleochroism:
Non-pleochroic
Chemistry of Cuatrocapaite-(K)
Mindat Formula:
K3(NaMg◻)(As2O3)6Cl6 · 16H2O
Element Weights:
Crystallography of Cuatrocapaite-(K)
Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R3m
Cell Parameters:
a = 5.2637(15) Å, c = 46.228(8) Å
Ratio:
a:c = 1 : 8.782
Unit Cell V:
1,109.22 ų (Calculated from Unit Cell)
Morphology:
Tablets, flattened on {001} and having hexagonal outlines. Forms: {001} and {100}; the pyramidal forms {10l} and {01l} are observed on some crystals.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 15.50 Å | (100) |
| 5.13 Å | (32) |
| 3.228 Å | (33) |
| 3.098 Å | (33) |
| 2.621 Å | (69) |
| 2.489 Å | (25) |
| 2.339 Å | (36) |
| 1.835 Å | (21) |
Reference:
Kampf, Anthony R., Chukanov, Nikita V., Möhn, Gerhard, Dini, Maurizio, Molina Donoso, Arturo A., Friis, Henrik (2019) Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite. Mineralogical Magazine, 83 (5) 741-748 doi:10.1180/mgm.2019.26
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] | |
| 47g : [Halogen-bearing surface weathering minerals] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 53 : Other minerals with taphonomic origins | <0.4 |
Type Occurrence of Cuatrocapaite-(K)
General Appearance of Type Material:
Hexagonal tablets flattened on {001}; the crystals are up to ca. 0.3 mm in diameter
Place of Conservation of Type Material:
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA, catalogue number 66987.
Geological Setting of Type Material:
secondary alteration
Associated Minerals at Type Locality:
Reference:
Kampf, Anthony R., Chukanov, Nikita V., Möhn, Gerhard, Dini, Maurizio, Molina Donoso, Arturo A., Friis, Henrik (2019) Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite. Mineralogical Magazine, 83 (5) 741-748 doi:10.1180/mgm.2019.26
Synonyms of Cuatrocapaite-(K)
Other Language Names for Cuatrocapaite-(K)
Dutch:Cuatrocapaiet-(K)
German:Cuatrocapait-(K)
Relationship of Cuatrocapaite-(K) to other Species
Member of:
Other Members of Lucabindiite Group:
| Cuatrocapaite-(NH4) | (NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2O | Trig. 3m(32/m) : R3m |
| Ermakovite | (NH4)(As2O3)2Br | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Gajardoite | KCa0.5As3+4O6Cl2 · 5H2O | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Gajardoite-(NH4) | (NH4)As3+4O6Cl2(Ca0.5◻0.5)(H2O)5 | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Lucabindiite | (K,NH4)As4O6(Cl,Br) | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Mauriziodiniite | (NH4)(As2O3)2I | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Russoite | (NH4)ClAs2O3(H2O)0.5 | Hex. 622 : P622 |
| Torrecillasite | Na(As,Sb)3+4O6Cl | Orth. |
Related Minerals - Strunz-mindat Grouping
| 3.DC. | Gajardoite | KCa0.5As3+4O6Cl2 · 5H2O |
| 3.DC. | Lucabindiite | (K,NH4)As4O6(Cl,Br) |
| 3.DC. | Dmitrievite | Sb4Cl2O5 |
| 3.DC. | Cuatrocapaite-(NH4) | (NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2O |
| 3.DC. | Napoliite | Pb2OFCl |
| 3.DC. | Torrecillasite | Na(As,Sb)3+4O6Cl |
| 3.DC.05 | Paralaurionite | PbCl(OH) |
| 3.DC.05 | Laurionite | PbCl(OH) |
| 3.DC.05 | Mauriziodiniite | (NH4)(As2O3)2I |
| 3.DC.05 | Russoite | (NH4)ClAs2O3(H2O)0.5 |
| 3.DC.10 | Fiedlerite | Pb3FCl4(OH) · H2O |
| 3.DC.15 | Penfieldite | Pb2Cl3(OH) |
| 3.DC.15 | Telluroperite | Pb3TeO4Cl2 |
| 3.DC.20 | Laurelite | Pb7F12Cl2 |
| 3.DC.25 | Zhangpeishanite | BaFCl |
| 3.DC.25 | Matlockite | PbFCl |
| 3.DC.25 | Zavaritskite | (BiO)F |
| 3.DC.25 | Rorisite | CaFCl |
| 3.DC.25 | Bismoclite | BiOCl |
| 3.DC.25 | Vegrandisite | BaCl2 |
| 3.DC.30 | Nadorite | PbSbClO2 |
| 3.DC.30 | Perite | PbBiClO2 |
| 3.DC.40 | Thorikosite | Pb3Cl2(OH)(SbO3,AsO3) |
| 3.DC.45 | Mereheadite | Pb47Cl25(OH)13O24(CO3)(BO3)2 |
| 3.DC.50 | Blixite | Pb8O5(OH)2Cl4 |
| 3.DC.52 | Rumseyite | Pb2OClF |
| 3.DC.55 | Vladkrivovichevite | [Pb32O18][Pb4Mn2O]Cl14(BO3)8 · 2H2O |
| 3.DC.55 | Pinalite | Pb3WO5Cl2 |
| 3.DC.57 | Yeomanite | Pb2O(OH)Cl |
| 3.DC.60 | Symesite | Pb10(SO4)O7Cl4 · H2O |
| 3.DC.60 | 'Lorettoite' | Pb7O6Cl2 |
| 3.DC.62 | 'Sarawakite (of Frenzel)' | Sb, O, Cl (?) |
| 3.DC.65 | Ecdemite | Pb6As3+2O7Cl4 |
| 3.DC.70 | Mendipite | Pb3Cl2O2 |
| 3.DC.75 | Damaraite | Pb3Cl(OH)O2 |
| 3.DC.80 | Onoratoite | Sb8Cl2O11 |
| 3.DC.95 | Barstowite | Pb4Cl6(CO3) · H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 6.3314% | 1,963 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Other Information
Notes:
At room temperature, not readily soluble in water or acids (including concentrated HCl, H2SO4 and HNO3); rapidly decomposes in aqueous solution of NaOH forming a nearly transparent residue of Mg(OH)2.
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 Cuatrocapaite-(K)
mindat.org URL:
https://www.mindat.org/min-53211.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 Cuatrocapaite-(K)
Reference List:
Hålenius, Ulf, Hatert, Frédéric, Pasero, Marco, Mills, Stuart J. (2018) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 46. European Journal of Mineralogy, 30 (6) 1181-1189 doi:10.1127/ejm/2018/0030-2819
Kampf, Anthony R., Chukanov, Nikita V., Möhn, Gerhard, Dini, Maurizio, Molina Donoso, Arturo A., Friis, Henrik (2019) Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite. Mineralogical Magazine, 83 (5) 741-748 doi:10.1180/mgm.2019.26
Localities for Cuatrocapaite-(K)
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.
Chile (TL) | |
| Kampf et al. (2019) |
Quick NavTopAbout Cuatrocapaite-(K)Unique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesRelationshipsStrunz-MindatRadioactivityOther InformationInternet Links References Localities Locality List
Torrecillas mine, Iquique, Iquique Province, Tarapacá, Chile