Bararite
A valid IMA mineral species - grandfathered
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About Bararite
Formula:
(NH4)2[SiF6]
Colour:
White; colourless in thin section
Lustre:
Vitreous
Hardness:
2½
Specific Gravity:
2.152
Crystal System:
Trigonal
Name:
For the locality at the Bararee colliery, Barari, Jharia coal field, India. The name was given by Palache et al. (1951) based on the description by Christie (1926). Earlier work recognized it as a constituent of mixtures with cryptohalite but it was not given an individual name.
Dimorph of:
A hexagonal polymorph (space group P63mc) is also known from synthetic material (Fábry et al. 2001).
Unique Identifiers
Mindat ID:
511
Long-form identifier:
mindat:1:1:511:7
IMA Classification of Bararite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
(NH4)2SiF6
First published:
1951
Classification of Bararite
3.CH.10
3 : HALIDES
C : Complex halides
H : Silicofluorides
3 : HALIDES
C : Complex halides
H : Silicofluorides
11.5.2.2
11 : HALIDE COMPLEXES
5 : AmBX6
11 : HALIDE COMPLEXES
5 : AmBX6
8.12.6
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)
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 |
|---|---|---|
| Brr | 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 Bararite
Vitreous
Transparency:
Transparent
Colour:
White; colourless in thin section
Streak:
White
Hardness:
2½ on Mohs scale
Cleavage:
Perfect
on {0001}
on {0001}
Density:
2.152 g/cm3 (Measured) 2.144 g/cm3 (Calculated)
Optical Data of Bararite
Type:
Uniaxial (-)
RI values:
nω = 1.406 nε = 1.391
Max. Birefringence:
δ = 0.015
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.
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.
Surface Relief:
Moderate
Chemistry of Bararite
Mindat Formula:
(NH4)2[SiF6]
Element Weights:
Elements listed:
Crystallography of Bararite
Crystal System:
Trigonal
Class (H-M):
3m (3 2/m) - Hexagonal Scalenohedral
Cell Parameters:
a = 5.77 Å, c = 4.78 Å
Ratio:
a:c = 1 : 0.828
Unit Cell V:
137.82 ų (Calculated from Unit Cell)
Z:
1
Morphology:
Minute crystals, flattened on {0001}, may be elongated perpendicular to [0001]; also arborescent and mammillary. Commonly included within cryptohalite.
Twinning:
Dartlike or paddlewheel twins, with twin plane inclined to {0001}
Comment:
Space Group: C3m - synthetic
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0012988 | Bararite | Schlemper E O, Hamilton W C (1966) On the structure of trigonal ammonium fluorosilicate Journal of Chemical Physics 45 408-409 | 1966 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.84 Å | (100) |
| 2.42 Å | (45) |
| 2.09 Å | (40) |
| 2.22 Å | (35) |
| 3.45 Å | (30) |
| 5.00 Å | (20) |
| 4.20 Å | (20) |
Comments:
Recorded on material from Kehley's Run Mine, Pennsylvania, USA
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Geological Setting:
Above burning coal seams; sublimation product at fumaroles and in burning anthracite piles.
Type Occurrence of Bararite
General Appearance of Type Material:
Arborescent, mammillary; commonly included within cryptohalite.
Place of Conservation of Type Material:
No defined type material.
Geological Setting of Type Material:
Above a burning coal seam.
Associated Minerals at Type Locality:
Synonyms of Bararite
Criptoalite (in part)
Other Language Names for Bararite
Common Associates
Associated Minerals Based on Photo Data:
| 3 photos of Bararite associated with Cryptohalite | (NH4)2[SiF6] |
| 3 photos of Bararite associated with Native Sulphur | S8 |
| 1 photo of Bararite associated with Coal |
Related Minerals - Strunz-mindat Grouping
| 3.CH.05 | Malladrite | Na2[SiF6] |
| 3.CH.15 | Hieratite | K2[SiF6] |
| 3.CH.15 | Cryptohalite | (NH4)2[SiF6] |
| 3.CH.20 | Demartinite | K2[SiF6] |
| 3.CH.25 | Knasibfite | K3Na4[SiF6]3[BF4] |
| 3.CH.30 | Heklaite | KNaSiF6 |
Other Information
Notes:
Easily soluble in water.
Sublimates without residue.
Tastes saline.
Sublimates without residue.
Tastes saline.
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 Bararite
mindat.org URL:
https://www.mindat.org/min-511.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Bararite
Reference List:
Localities for Bararite
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 | |
| Žáček et al. (1998) |
Germany | |
| Walenta (1992) |
India (TL) | |
| Palache et al. (1951) +1 other reference |
Italy | |
| Palache et al. (1951) +1 other reference |
| Palache et al. (1951) +2 other references | |
| - (n.d.) |
| - (n.d.) |
| Montrasio et al. (1996) | |
Poland | |
| Kruszewski (2012) |
USA | |
| |
| Montgomery (Sep 1972) +2 other references |
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Kateřina Coal Mine, Radvanice, Trutnov District, Hradec Králové Region, Czech Republic