Bøgvadite
A valid IMA mineral species
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Richard Bøgvad
Formula:
Na2SrBa2Al4F20
Colour:
Colourless
Lustre:
Vitreous
Hardness:
4
Specific Gravity:
3.85
Crystal System:
Monoclinic
Name:
Named in honor of Richard Bøgvad (21 November 1897, Frederiksberg, Denmark - 7 August 1952, Ivigtut, Greenland), formerly Chief Geologist for the company Oresund A/S, which mined the Ivigtut cryolite deposit.
This page provides mineralogical data about Bøgvadite.
Name Encoding
ASCII-7:
Bogvadite
Unique Identifiers
Mindat ID:
705
Long-form identifier:
mindat:1:1:705:4
IMA Classification of Bøgvadite
Approved
IMA Formula:
Na2Ba2SrAl4F20
Approval year:
1987
First published:
1988
Classification of Bøgvadite
3.CF.15
3 : HALIDES
C : Complex halides
F : Tekto-aluminofluorides
3 : HALIDES
C : Complex halides
F : Tekto-aluminofluorides
11.6.20.1
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
8.4.18
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
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 |
|---|---|---|
| Bgv | 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 Bøgvadite
Vitreous
Transparency:
Transparent
Colour:
Colourless
Streak:
White
Hardness:
4 on Mohs scale
Hardness:
VHN25=300 - 350 kg/mm2 - Vickers
Fracture:
Irregular/Uneven
Density:
3.85 g/cm3 (Measured) 3.898 g/cm3 (Calculated)
Optical Data of Bøgvadite
Type:
Biaxial (-)
RI values:
nα = 1.4326 nβ = 1.436 nγ = 1.4389
2V:
Measured: 87° , Calculated: 85°
Max. Birefringence:
δ = 0.006
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:
High (negative)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
Weak
Chemistry of Bøgvadite
Mindat Formula:
Na2SrBa2Al4F20
Element Weights:
Crystallography of Bøgvadite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 7.134(1) Å, b = 19.996(3) Å, c = 5.3440(8) Å
β = 90.02(1)°
β = 90.02(1)°
Ratio:
a:b:c = 0.357 : 1 : 0.267
Unit Cell V:
762.33 ų (Calculated from Unit Cell)
Morphology:
Blocky crystals, showing {110}, {010} and {012}, slightly flattened on {010} and elongated parallel to [100], with rounded and corroded faces.
Comment:
Space group P21/n. Pseudo-orthorhombic.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.240 Å | (100) |
| 3.194 Å | (50) |
| 2.924 Å | (50) |
| 2.116 Å | (50) |
| 9.968 Å | (40) |
| 6.689 Å | (40) |
| 2.668 Å | (40) |
Reference:
Comments:
Recorded on type material
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47) | |
| 25 : Evaporites (prebiotic) |
Type Occurrence of Bøgvadite
General Appearance of Type Material:
Blocky crystals to 0.15 mm, with rounded and corroded faces.
Place of Conservation of Type Material:
University of Copenhagen, Geological Museum, Copenhagen, Denmark, numbers 1989.172, 1989.173.
Geological Setting of Type Material:
Cryolite deposit
Associated Minerals at Type Locality:
Synonyms of Bøgvadite
Other Language Names for Bøgvadite
Related Minerals - Strunz-mindat Grouping
| 3.CF.05 | Hydrokenoralstonite | Na0.5(Al,Mg)2(F,OH)6 · H2O |
| 3.CF.10 | 'UM1941-01-F:AlCaHMgNa' | NaCaMgAl3F14 · 4H2O |
Other Information
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 Bøgvadite
mindat.org URL:
https://www.mindat.org/min-705.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Bøgvadite
Reference List:
Pauly, Hans; Petersen, Ole V. (1988) Bøgvadite, Na2SrBa2Al4F20, a new fluoride from the cryolite deposit, Ivigtut, S. Greenland. Bulletin of the Geological Society of Denmark, 37. 21-30 doi:10.37570/bgsd-1988-37-03
Localities for Bøgvadite
Showing 1 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.
Greenland (TL) | |
| Pauly et al. (1988) +2 other references |
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