Koktaite
A valid IMA mineral species - grandfathered
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About Koktaite
Formula:
(NH4)2Ca(SO4)2 · H2O
Colour:
Colourless, white
Specific Gravity:
2.09
Crystal System:
Monoclinic
Name:
Named in honor of Jaroslav Kokta (29 April 1904, Skorotice, Austria-Hungary - 2 August 1970, Ostrava, Czechoslovakia), chemist at the Masarykov University, Brno, Czechoslovakia who analyzed the artificial compound.
This page provides mineralogical data about Koktaite.
Unique Identifiers
Mindat ID:
2237
Long-form identifier:
mindat:1:1:2237:4
IMA Classification of Koktaite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
(N3-H4)2Ca(S6+O4)2·H2O
First published:
1948
Classification of Koktaite
7.CD.35
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
D : With only large cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
D : With only large cations
29.3.1.2
29 : HYDRATED ACID AND NORMAL SULFATES
3 : A2B(XO4)2·xH2O
29 : HYDRATED ACID AND NORMAL SULFATES
3 : A2B(XO4)2·xH2O
25.4.11
25 : Sulphates
4 : Sulphates of Ca, Sr and Ba
25 : Sulphates
4 : Sulphates of Ca, Sr and Ba
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 |
|---|---|---|
| Kkt | 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 Koktaite
Transparency:
Transparent, Translucent
Colour:
Colourless, white
Streak:
White
Cleavage:
None Observed
Density:
2.09 g/cm3 (Measured) 2.114 g/cm3 (Calculated)
Optical Data of Koktaite
Type:
Biaxial (-)
RI values:
nα = 1.524 nβ = 1.532 nγ = 1.536
2V:
Measured: 72° , Calculated: 70°
Max. Birefringence:
δ = 0.012
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:
Moderate
Dispersion:
r > v
Comments:
Y = b; Z' ∧ c (on {110})=2◦
Chemistry of Koktaite
Mindat Formula:
(NH4)2Ca(SO4)2 · H2O
Element Weights:
Crystallography of Koktaite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/a
Cell Parameters:
a = 10.17 Å, b = 7.15 Å, c = 6.34 Å
β = 102.75°
β = 102.75°
Ratio:
a:b:c = 1.422 : 1 : 0.887
Unit Cell V:
449.65 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals acicular or fibrous-lamellar.
Forms: {100}, {110}, {001}, {011}, {101}
Forms: {100}, {110}, {001}, {011}, {101}
Twinning:
On {100}, common.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.83 Å | (100) |
| 3.30 Å | (65) |
| 4.96 Å | (40) |
| 5.83 Å | (25) |
| 3.00 Å | (25) |
| 3.56 Å | (20) |
| 2.89 Å | (20) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 21 : Chemically precipitated carbonate, phosphate, iron formations | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] | |
| 45b : [Other oxidized fumarolic minerals] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| 52 : Guano- and urine-derived minerals | <0.4 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Type Occurrence of Koktaite
General Appearance of Type Material:
Pseudomorphs after gypsum.
Place of Conservation of Type Material:
1) Moravian Museum, Brno, Czech Republic, A6109.
2) National School of Mines, Paris, France.
3) National Museum of Natural History, Washington, D.C., USA, 137963.
2) National School of Mines, Paris, France.
3) National Museum of Natural History, Washington, D.C., USA, 137963.
Geological Setting of Type Material:
Waste piles of a lignite mine.
Associated Minerals at Type Locality:
Synonyms of Koktaite
Other Language Names for Koktaite
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 7.CD. | Argesite | (NH4)7Bi3Cl16 |
| 7.CD. | Campostriniite | (Bi3+,Na)3(NH4,K)2Na2(SO4)6 · H2O |
| 7.CD.05 | Matteuccite | NaHSO4 · H2O |
| 7.CD.10 | Mirabilite | Na2SO4 · 10H2O |
| 7.CD.15 | Lecontite | (NH4)Na(SO4) · 2H2O |
| 7.CD.20 | Hydroglauberite | Na10Ca3(SO4)8 · 6H2O |
| 7.CD.25 | Eugsterite | Na4Ca(SO4)3 · 2H2O |
| 7.CD.30 | Görgeyite | K2Ca5(SO4)6 · H2O |
| 7.CD.35 | Syngenite | K2Ca(SO4)2 · H2O |
| 7.CD.35 | Antofagastaite | Na2Ca(SO4)2 · 1.5H2O |
| 7.CD.40 | Gypsum | CaSO4 · 2H2O |
| 7.CD.45 | Chinleite-(Y) | NaY(SO4)2 · H2O |
| 7.CD.45 | Bassanite | Ca(SO4) · 0.5H2O |
| 7.CD.45 | Chinleite-(Nd) | NaNd(SO4)2 · H2O |
| 7.CD.45 | Chinleite-(Ce) | NaCe(SO4)2(H2O) |
| 7.CD.50 | Zircosulfate | (Zr,Ti)(SO4)2 · 4H2O |
| 7.CD.55 | Schieffelinite | Pb10Te6+6O20(OH)14(SO4)(H2O)5 |
| 7.CD.60 | Montanite | Bi2(TeO6) · nH2O |
| 7.CD.65 | Omongwaite | Na2Ca5(SO4)6 · 3H2O |
Other Information
Notes:
Soluble in H2O, leaving a residue of gypsum.
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 Koktaite
mindat.org URL:
https://www.mindat.org/min-2237.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 Koktaite
Reference List:
Localities for Koktaite
Showing 18 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.
Czech Republic | |
| Matýsek et al. (2022) |
| Matýsek et al. (2022) | |
| Dr. Jaroslav Hyrsl labels |
| Sekanina (1948) +1 other reference |
Germany | |
| Witzke et al. (1998) |
Ghana | |
| Addae et al. (2026) |
Hungary | |
| Szakáll et al. (2008) |
| Szakáll et al. (1997) |
New Zealand | |
| Johnstone (1979) |
| Johnstone (1979) | |
Poland | |
| Ł. Kruszewski (PXRD data) |
| Kruszewski et al. (2018) |
Russia | |
| Cesnokov et al. (1998) |
USA | |
| Adams et al. (2014) |
| Adams et al. (2014) | |
| Kampf et al. (2024) |
Venezuela | |
| Urbani |
| Franco Urbani (2009) |
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Zastávka coal dumps, Zastávka, Brno-Country District, South Moravian Region, Czech Republic