Cryolite
A valid IMA mineral species - grandfathered
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About Cryolite
Formula:
Na2NaAlF6
Colour:
Colourless, white, brown, grey, black; colourless in transmitted light.
Lustre:
Vitreous, Greasy, Pearly
Hardness:
3 - 3½
Specific Gravity:
2.96 - 2.98
Crystal System:
Monoclinic
Member of:
Name:
From the Greek κρύος, frost, and λίθος, stone, meaning "ice-stone" in allusion to its appearance.
A curiosity mineral. Colourless samples of this sodium-aluminium-fluoride mineral seemingly disappear in water due to the proximity of their refractive indices.
Historically, cryolite was used as an aluminium ore and later in the electrolytic processing of the aluminium ore bauxite.
Historically, cryolite was used as an aluminium ore and later in the electrolytic processing of the aluminium ore bauxite.
Visit gemdat.org for gemological information about Cryolite.
Unique Identifiers
Mindat ID:
1161
Long-form identifier:
mindat:1:1:1161:3
GUID
(UUID V4):
(UUID V4):
2aad8b81-c8be-490e-86f0-f03110dae967
IMA Classification of Cryolite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1799
Classification of Cryolite
3.CB.15
3 : HALIDES
C : Complex halides
B : Neso-aluminofluorides
3 : HALIDES
C : Complex halides
B : Neso-aluminofluorides
11.6.1.1
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
8.6.5
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.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Symbol | Source | Reference |
---|---|---|
Crl | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Crl | Whitney & Evans (2010) | Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187 doi:10.2138/am.2010.3371 |
Cry | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of Cryolite
Vitreous, Greasy, Pearly
Transparency:
Transparent, Translucent
Comment:
Pearly on {001}
Colour:
Colourless, white, brown, grey, black; colourless in transmitted light.
Streak:
White
Hardness:
3 - 3½ on Mohs scale
Hardness:
VHN50=286 - 412 kg/mm2 - Vickers
Comment:
Normally published values of Mohs 2.5-3 are for massive material; crystals are harder. Vickers values are for (100). A full discussion is given in Pauly (1985).
Tenacity:
Brittle
Cleavage:
None Observed
Parting:
On {001} and {110}, producing cuboidal forms.
Fracture:
Irregular/Uneven
Density:
2.96 - 2.98 g/cm3 (Measured) 2.973(2) g/cm3 (Calculated)
Optical Data of Cryolite
Type:
Biaxial (+)
RI values:
nα = 1.339 - 1.339 nβ = 1.339 - 1.339 nγ = 1.340 - 1.340
2V:
Measured: 43°
Max Birefringence:
δ = 0.001
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r < v
Optical Extinction:
X = b; Z ∧ c = −44°.
Chemistry of Cryolite
Mindat Formula:
Na2NaAlF6
Elements listed:
Common Impurities:
Fe,Ca
Crystallography of Cryolite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 7.7564(3) Å, b = 5.5959(2) Å, c = 5.4024(2) Å
β = 90.18°
β = 90.18°
Ratio:
a:b:c = 1.386 : 1 : 0.965
Unit Cell V:
234.48 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals usually cuboidal with c, , or modified by r, v, k; also short prismatic [001]. {110} faces striated [111], [111], or [110]. Massive, coarsely granular.
Twinning:
Very common. Often repeated or polysynthetic with simultaneous occurrence of several twin laws, and reflecting the pseudo-orthorhombic symmetry of the unit cell.
1. By a 90° or 270° rotation on [110], penetration, common.
2. By a 180° rotation on [110], rhombic section (110), repeated, less common.
3. By a 120° rotation on [021], composition surface irregular; common, especially in granular material, as fine lamellae and probably always secondary.
4. By a 180° rotation on [111], rhombic section near (110), repeated; rare (not in granular material).
5. On (001) or by a 180° rotation on [100], composition plane (001).
6. On (100) or by a 180° rotation on [001], composition plane (100).
7. On (112), composition plane (112).
8. On (112), composition plane (112).
9. On (110), composition plane (110).
10. By a 180° rotation on [111], rhombic section near (110).
11. On (211).
(Palache et al (1951), Dana's System of Mineralogy, 7th. ed., vol. 2: 111).
1. By a 90° or 270° rotation on [110], penetration, common.
2. By a 180° rotation on [110], rhombic section (110), repeated, less common.
3. By a 120° rotation on [021], composition surface irregular; common, especially in granular material, as fine lamellae and probably always secondary.
4. By a 180° rotation on [111], rhombic section near (110), repeated; rare (not in granular material).
5. On (001) or by a 180° rotation on [100], composition plane (001).
6. On (100) or by a 180° rotation on [001], composition plane (100).
7. On (112), composition plane (112).
8. On (112), composition plane (112).
9. On (110), composition plane (110).
10. By a 180° rotation on [111], rhombic section near (110).
11. On (211).
(Palache et al (1951), Dana's System of Mineralogy, 7th. ed., vol. 2: 111).
Comment:
Spacegroup: P21/n (Mitchell et al. 2016); at 5K, the structure is the same as that at RT
Crystallographic forms of Cryolite
Crystal Atlas:
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
---|---|---|---|---|---|---|---|
0005118 | Cryolite | Hawthorne F C, Ferguson R B (1975) Refinement of the crystal structure of cryolite The Canadian Mineralogist 13 377-382 | 1975 | 0 | 293 | ||
0007739 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007740 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007741 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007742 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007743 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007744 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007745 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007746 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007747 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007748 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007749 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0007750 | Cryolite | Yang H, Ghose S, Hatch D M (1993) Ferroelastic phase transition in cryolite, Na3AlF6, a mixed fluoride perovskite: high temperature single crystal X-ray diffraction study and symmetry analysis of the transition mechanism Physics and Chemistry of Minerals 19 528-544 | 1993 | 0 | 293 | ||
0017654 | Cryolite | Naray-Szabo S, Sasvari K (1938) Die Struktur des Kryoliths Na3 Al F6 _cod_database_code 1010932 Zeitschrift fur Kristallographie 99 27-31 | 1938 | 0 | 293 | ||
0014033 | Cryolite | Ross K C, Mitchell R H, Chakhmouradian A R (2003) The crystal structure of synthetic simmonsite, Na2LiAlF6 Journal of Solid State Chemistry 172 95-101 | 2003 | natural | 0 | 293 | |
0014034 | Cryolite | Ross K C, Mitchell R H, Chakhmouradian A R (2003) The crystal structure of synthetic simmonsite, Na2LiAlF6 Journal of Solid State Chemistry 172 95-101 | 2003 | synthetic | 0 | 293 | |
0014038 | Cryolite | Zhou Q, Kennedy B J (2004) High-temperature powder synchrotron diffraction studies of synthetic cryolite Na3AlF6 Journal of Solid State Chemistry 177 654-659 | 2004 | synthetic | 0 | 293 | |
0014039 | Cryolite | Zhou Q, Kennedy B J (2004) High-temperature powder synchrotron diffraction studies of synthetic cryolite Na3AlF6 Journal of Solid State Chemistry 177 654-659 | 2004 | synthetic | 0 | 293 | |
0014040 | Cryolite | Zhou Q, Kennedy B J (2004) High-temperature powder synchrotron diffraction studies of synthetic cryolite Na3AlF6 Journal of Solid State Chemistry 177 654-659 | 2004 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
Epitaxial Relationships of Cryolite
Epitaxial Minerals:
Thénardite | Na2SO4 |
Epitaxy Comments:
Oriented growths (artificial material).
X-Ray Powder Diffraction
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Radiation - Copper Kα
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
d-spacing | Intensity |
---|---|
2.748 Å | (100) |
1.943 Å | (95) |
3.886 Å | (65) |
4.54 Å | (55) |
4.44 Å | (40) |
1.571 Å | (35) |
2.337 Å | (30) |
Comments:
Synthetic. ICDD 25-772.
Geological Environment
Paragenetic Mode(s):
Paragenetic Mode | Earliest Age (Ga) |
---|---|
Near-surface Processes | |
24 : Authigenic minerals in terrestrial sediments (see also #17) | |
Stage 4b: Highly evolved igneous rocks | >3.0 |
34 : Complex granite pegmatites | |
35 : Ultra-alkali and agpaitic igneous rocks | |
36 : Carbonatites, kimberlites, and related igneous rocks | |
Stage 7: Great Oxidation Event | <2.4 |
45b : [Other oxidized fumarolic minerals] |
Geological Setting:
Late stage mineral in granitic pegmatites, vapor phase mineral in rhyolites.
Type Occurrence of Cryolite
General Appearance of Type Material:
Massive white transparent to translucent.
Place of Conservation of Type Material:
University of Copenhagen, Denmark
Geological Setting of Type Material:
As a pegmatitic body in a granite stock intruded into gneiss.
Associated Minerals at Type Locality:
Synonyms of Cryolite
Other Language Names for Cryolite
Asturian:Criolita
Catalan:Criolita
Czech:Kryolit
Danish:Kryolit
Dutch:Cryoliet
Estonian:Krüoliit
Hebrew:קריאוליט
Italian:Criolite
Japanese:氷晶石
Norwegian:Kryolitt
Norwegian (Nynorsk):Kryolitt
Polish:Kriolit
Portuguese:Criolita
Russian:Криолит
Serbian:Криолит
Simplified Chinese:冰晶石
Slovenian:Kriolit
Spanish:Criolita
Sundanese:Kriolit
Ukrainian:Кріоліт
Vietnamese:Cryôlit
Relationship of Cryolite to other Species
Member of:
Other Members of this group:
Elpasolite | K2NaAlF6 | Iso. m3 (2/m 3) : Pa3 |
Simmonsite | Na2LiAlF6 | Mon. |
Common Associates
Associated Minerals Based on Photo Data:
125 photos of Cryolite associated with Siderite | FeCO3 |
73 photos of Cryolite associated with Thomsenolite | NaCa[AlF6] · H2O |
25 photos of Cryolite associated with Chalcopyrite | CuFeS2 |
24 photos of Cryolite associated with Galena | PbS |
21 photos of Cryolite associated with Fluorite | CaF2 |
20 photos of Cryolite associated with Quartz | SiO2 |
18 photos of Cryolite associated with Hydrokenoralstonite | Na0.5(Al,Mg)2(F,OH)6 · H2O |
16 photos of Cryolite associated with Pachnolite | NaCa[AlF6] · H2O |
15 photos of Cryolite associated with Cryolithionite | Na3Al2(LiF4)3 |
14 photos of Cryolite associated with Topaz | Al2(SiO4)(F,OH)2 |
Related Minerals - Strunz-mindat Grouping
3.CB.05 | Cryolithionite | Na3Al2(LiF4)3 |
3.CB.15 | Elpasolite | K2NaAlF6 |
3.CB.15 | Simmonsite | Na2LiAlF6 |
3.CB.20 | Colquiriite | CaLi[AlF6] |
3.CB.25 | Weberite | Na2Mg[AlF6]F |
3.CB.25 | Leonardsenite | MgAlF5 · 2H2O |
3.CB.30 | Karasugite | SrCa[Al(F,OH)7] |
3.CB.35 | Usovite | Ba2CaMgAl2F14 |
3.CB.40 | Pachnolite | NaCa[AlF6] · H2O |
3.CB.40 | Thomsenolite | NaCa[AlF6] · H2O |
3.CB.45 | Carlhintzeite | Ca2[AlF6]F · H2O |
3.CB.50 | Yaroslavite | Ca3Al2F10(OH)2 · H2O |
3.CB.55 | Sbacchiite | Ca2AlF7 |
3.CB.60 | Verneite | Na2Ca3Al2F14 |
Other Information
Thermal Behaviour:
Melting Point: 1020°. Inverts to an isometric form at about 560°. Weakly thermoluminescent.
Notes:
Soluble in H2SO4 with evolution of HF. Slightly soluble in water. Readily soluble in AlCl3 solution.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Synthetically produced material is an important electrolyte for the production of aluminium from bauxite (Bayer and Hall–Héroult processes).
Internet Links for Cryolite
mindat.org URL:
https://www.mindat.org/min-1161.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 Cryolite
Localities for Cryolite
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).
Struck out - Mineral was erroneously reported from this locality.
Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.
All localities listed without proper references should be considered as questionable.
Brazil | |
| Horbe et al. (1991) |
Horbe et al. (1999) +4 other references | |
| G. Traversa et al. +1 other reference |
Canada | |
| 166-175. +2 other references |
| Horváth et al. (1998) |
Horváth et al. (1998) | |
| 176-178. +2 other references |
Czech Republic | |
| Bull. Minéral. |
| Bull. Minéral. |
Europe | |
| Bull. Minéral. |
Greenland | |
| Pauly (1946) |
| Breiter et al. (2024) |
| Scherer's Allg. Journal D. Chemie (1799) +2 other references |
Kazakhstan | |
| Pavel.M. Kartashov (n.d.) +1 other reference |
Mali | |
| Liégeois et al. (1984) +3 other references |
Namibia | |
| Uwe Kolitsch (single-crystal X-ray diffraction) +3 other references |
| American Mineralogist +1 other reference |
Buhn et al. (2002) | |
Nigeria | |
| 44-61 Earth Sciences Research Journal +4 other references |
| Bailey |
Am Min 51:299-323 | |
Bailey | |
Bailey | |
Bailey | |
Norway | |
| Eldjarn (1981) +1 other reference |
Poland | |
| Łukasz Kruszewski (2012) |
Romania | |
| Hirtopanu (2006) |
Russia | |
| Bailey +2 other references |
| Bailey +1 other reference |
| ... |
Volume 2: Minerals [Минералы]. Nauka et al. (in Russian) +6 other references | |
... +1 other reference | |
| Pekov (1998) +1 other reference |
| Pekov et al. (2008) |
| Bailey |
| Bailey |
Pavel.M. Kartashov (n.d.) +1 other reference | |
| USGS Open File Report 2005-1252 p20 +5 other references |
Saint Helena, Ascension and Tristan da Cunha | |
Bailey | |
Spain | |
| Am Min 51:299-323 |
| Dill et al. (2023) |
Dill et al. (2023) | |
Ukraine | |
| Sharygin (2015) |
| Bailey +2 other references |
| Bailey +2 other references |
USA | |
| David London et al. (2016) |
| Eckel et al. (1997) |
| - (2005) |
- (2005) | |
Palache et al. (1951) +1 other reference | |
Gross et al. (1966) | |
Gross et al. (1966) | |
Landes (1935) +1 other reference | |
- (2005) | |
| Armbrustmacher (1988) +1 other reference |
Eckel et al. (1997) | |
Eckel et al. (1997) | |
Eckel et al. (1997) | |
| Eckel et al. (1997) |
| Meeves et al. (1966) |
| Eckel et al. (1997) |
Tank (1972) +2 other references | |
| Mineralogical Record: 31: 204. |
| |
| DeMark (1989) +1 other reference |
| Am. Min. 74:865-869 (1989) |
Am Min 72:1122-1130 +2 other references | |
| Bullock (1981) |
| Kearns (1995) +1 other reference |
| Rocks & Min. (2007) |
Bailey |
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Ivigtut Mine, Ivigtut stock, Arsuk Fjord, Sermersooq, Greenland