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Cryptohalite

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Formula:
(NH4)2[SiF6]
System:
Isometric
Colour:
Colourless, white, grey; ...
Lustre:
Vitreous
Hardness:
Name:
From the Greek κρυπτός, concealed, and άλς, salt, in allusion to its intimate mixture with salammoniac in the type locality occurrence.
Dimorph of:
Isostructural with:
This page provides mineralogical data about Cryptohalite.

Classification of Cryptohalite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
3.CH.15

3 : HALIDES
C : Complex halides
H : Silicofluorides
11.5.1.2

11 : HALIDE COMPLEXES
5 : AmBX6
8.12.5

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)
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First Recorded Occurrence of Cryptohalite

Year of Discovery:
1873
Associated Minerals at First Recorded Locality:

Physical Properties of Cryptohalite

Vitreous
Colour:
Colourless, white, grey; colourless in transmitted light
Hardness (Mohs):
Cleavage:
Perfect
on {111}
Density:
2.004 g/cm3 (Measured)    2.029 g/cm3 (Calculated)

Crystallography of Cryptohalite

Crystal System:
Isometric
Class (H-M):
m3m (4/m 3 2/m) - Hexoctahedral
Space Group:
Fm3m
Cell Parameters:
a = 8.39Å
Unit Cell Volume:
V 590.59 ų (Calculated from Unit Cell)
Morphology:
Artificial crystals are cubo-octahedral and octahedral. Massive, as lumps with a mammillary surface or crusts; arborescent.

Optical Data of Cryptohalite

Type:
Isotropic

Chemical Properties of Cryptohalite

Formula:
(NH4)2[SiF6]
Essential elements:
All elements listed in formula:

Relationship of Cryptohalite to other Species

3.CH.05MalladriteNa2[SiF6]
3.CH.10Bararite(NH4)2[SiF6]
3.CH.15HieratiteK2[SiF6]
3.CH.20DemartiniteK2[SiF6]
3.CH.25KnasibfiteK3Na4[SiF6]3[BF4]
8.12.1FerrucciteNa[BF4]
8.12.2Avogadrite(K,Cs)[BF4]
8.12.3MalladriteNa2[SiF6]
8.12.4HieratiteK2[SiF6]
8.12.6Bararite(NH4)2[SiF6]

Other Names for Cryptohalite

Name in Other Languages:

Other Information

Other Information:
Soluble in cold water, more so in hot water.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Cryptohalite

Reference List:
Scacchi (1873) Reale accademia delle scienze fisische e matematiche, Naples, Att,: 6, no. 9 (as Criptoalite).

Topsøe (1874) Annales de chimie et de physique, Paris: 1: 22.

Gossner (1903) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 38: 147.

Bozorth (1922) American Chemical Society Journal: 44: 1066.

Christie (1926) Rec. Geol. Survey India: 59: 233.

Ketelaar (1935) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 92: 155.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 104-105.

Journal of Chemical Physics: 44: 2499-2505.

Internet Links for Cryptohalite

Localities for Cryptohalite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Czech Republic
 
  • Bohemia (Böhmen; Boehmen)
    • Central Bohemia Region
Zacek, V., Oplustil, S., Mayova, A. & Meyer, F. R. (1995): Die Mineralien von Kladno in Mittelböhmen, Tschechische Republik. Mineralien-Welt 6 (1), 13-30 (in German).
Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume 2: 105.
David Parfitt collection
    • Hradec Králové Region
      • Trutnov (Trautenau)
        • Radvanice
Žáček, V., Ondruš, P.: Mineralogy of recently formed sublimates from Kateřina colliery in Radvanice, Eastern Bohemia, Czech Republic. Bulletin of the Czech geological survey, 1998, vol. 73, no. 2, s. 289-302.
        • Žacléř
Harapát, L.: Minerály hořících hald dolu Jan Šverma u Žacléře. Časopis pro mineralogii a geologii, 1986, roč. 31, č. 1, s. 99-100.
Germany
 
  • Baden-Württemberg
    • Black Forest
      • Wolfach
        • Oberwolfach
          • Rankach valley
Walenta, K. (1992): Die Mineralien des Schwarzwaldes. Chr. Weise Verlag, München, 336 pp. (in German)
  • North Rhine-Westphalia
    • Aachen
      • Alsdorf
XRD and EDX-analysed by Günter Blaß
India
 
  • Bihar
    • Jharia Coalfield
Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume 2: 105.
Italy
 
  • Campania
    • Naples Province
      • Somma-Vesuvius Complex
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 105; Lapis (1994): 5: 13-23, 58.
Saint Helena
 
Bailey, J. C: Formation of cryolite and other aluminofluorides: A petrologic review. Bull. geol. Soc. Denmark, vol. 29, pp. 1-45. Copenhagen, June 10th, 1980
Tajikistan
 
  • Viloyati Sogd (Viloyati Sughd; Viloyati Khodzhent; Viloyati Leninabad)
    • Zeravshan Range
      • Yagnob River
PXRD
USA
 
  • Pennsylvania
    • Columbia Co.
    • Schuylkill Co.
      • Shenandoah
Reed, Juliet C. (1976), Annotated Biblio. of Minerals New to the Pennsylvania List 1965-1974, The Mineralogical Society of PA, Inc.: 29-30; Finkelman, et al, Geol. Soc. Am. Abstracts with Programs, Vol. 5(1): 27-28.
Mineral and/or Locality  
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