Cryptohalite Mineral Data

Cryptohalite Mineral Data

General Cryptohalite Information

Chemical Formula:

(NH4)2SiF6

Composition:

Molecular Weight = 178.15 gm

Silicon 15.76 % Si 33.73 % SiO₂

Hydrogen 4.53 % H - % Calc as (NH₄)₂O

Nitrogen 15.72 % N 29.23 % (NH₄)₂O

Fluorine 63.98 % F 63.98 % F

- % F -26.94 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

(NH₄)₂SiF₆

IMA Status:

Valid Species (Pre-IMA) 1873

Locality:

Link to MinDat.org Location Data.

Synonym:

ICSD 18033

PDF 44-1484

Cryptohalite Image

Images:

Cryptohalite

Comments: White to colorless crystals of cryptohalite. The red color is due to admixtured (amorphous ?) selenium.
Location: Kladno, Stredocesk? Kraj, Bohemia, Czech Republic. Scale: Picture size 5 mm.
© Thomas Witzke / Abraxas-Verlag

Images:

Cryptohalite Bararite

Comments: White crystalline bararite intermixed with cryptohalite colored yellow by selenium.
Location: Shamokin, Northumberland County, Pennsylvani, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Cryptohalite Crystallography

Cell Dimensions:

a = 8.395, Z = 4; V = 591.65 Den(Calc)= 2.00

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F m3m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 4.844(1), 2.422(0.45), 2.098(0.35),

Crystal Structure:

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Schlemper E O , Hamilton W C , Rush J J , Journal of Chemical Physics , 44 (1966) p.2499-2505, Structure of cubic ammonium fluosilicate: Neutron-diffraction and, neutron-inelastic-scattering studies, Locality: synthetic

Physical Properties of Cryptohalite

Cleavage:

[111] Perfect

Color:

Colorless, Gray, White.

Density:

2.011

Diaphaniety:

Transparent

Hardness:

2.5 - Finger Nail

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Cryptohalite

Gladstone-Dale:

CI meas= -0.831 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.841 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1845,KPDmeas= 0.1835,KC= 0.1002

Optical Data:

Isotropic, n=1.369.

Calculated Properties of Cryptohalite

Electron Density:

r_electron=2.03 gm/cc
note: r_Cryptohalite=2.01 gm/cc.

Fermion Index

Fermion Index = 0.16403
Boson Index = 0.83597

Photoelectric:

PE_Cryptohalite= 0.97 barns/electron
U=PE_Cryptohalite x r_electron= 1.97 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cryptohalite is Not Radioactive

Cryptohalite Classification

Dana Class:

11.5.1.2 (11)Halide Complexes; Alumino-fluorides

(11.5)where (A)m B (X)6

(11.5.1)Dana Group

11.5.1.1. Hieratite K2SiF6 F m3m 4/m 3 2/m

11.5.1.2 Cryptohalite (NH4)2SiF6 F m3m 4/m 3 2/m

Strunz Class:

III/B.02-30 III - Halogenides

III/B - Double halogenides without water, with [BF4]1-,[SiF6]2- and [AlF6]3-

III/B.02 - Mallardite - Bararite series

III/B.02-10 Malladrite Na2SiF6 P 3₂1 3 2

III/B.02-20 Hieratite K2SiF6 F m3m 4/m 3 2/m

III/B.02-30 Cryptohalite (NH4)2SiF6 F m3m 4/m 3 2/m

III/B.02-40 Bararite (NH4)2SiF6 R 3m 3 2/m

Other Cryptohalite Information

References:

PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Cryptohalite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 - EUROmin Project 4 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 -École des Mines de Paris

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Print or Cut-and-Paste your Cryptohalite Specimen Label here :

Cryptohalite

(NH4)2SiF6
Dana No: 11.5.1.2 Strunz No: III/B.02-30
Locality:

Notes: