Aksaite
A valid IMA mineral species
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About Aksaite
Formula:
Mg[B6O7(OH)6] · 2H2O
Colour:
Colorless, white to pale gray
Hardness:
2½
Specific Gravity:
2.066
Crystal System:
Orthorhombic
Name:
Named after its discovery locality in Kazakhstan.
This page provides mineralogical data about Aksaite.
Unique Identifiers
Mindat ID:
73
Long-form identifier:
mindat:1:1:73:0
Similar Names
IMA Classification of Aksaite
Approved
IMA Formula:
MgB6O7(OH)6·2H2O
First published:
1962
Classification of Aksaite
6.FA.05
6 : BORATES
F : Hexaborates
A : Neso-hexaborates
6 : BORATES
F : Hexaborates
A : Neso-hexaborates
26.6.4.1
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
9.2.6
9 : Borates
2 : Borates of Be and Mg
9 : Borates
2 : Borates of Be 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 |
|---|---|---|
| Aks | 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 Aksaite
Transparency:
Transparent, Translucent
Colour:
Colorless, white to pale gray
Streak:
White
Hardness:
2½ on Mohs scale
Cleavage:
Distinct/Good
Probable on {100} and {010} .
Probable on {100} and {010} .
Density:
2.066 g/cm3 (Measured) 1.972 g/cm3 (Calculated)
Optical Data of Aksaite
Type:
Biaxial (-)
RI values:
nα = 1.473(1) nβ = 1.508(1) nγ = 1.528(1)
2V:
Measured: 88° , Calculated: 78°
Max. Birefringence:
δ = 0.055
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:
Moderate (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:
none
Chemistry of Aksaite
Mindat Formula:
Mg[B6O7(OH)6] · 2H2O
Element Weights:
Elements listed:
Crystallography of Aksaite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pbca
Cell Parameters:
a = 12.54 Å, b = 24.35 Å, c = 7.48 Å
Ratio:
a:b:c = 0.515 : 1 : 0.307
Unit Cell V:
2,284.01 ų (Calculated from Unit Cell)
Morphology:
Crystals are elongated along [001] and flattened {100} , with {100} , {010} , {021} and rarely {001} , to 1.5 cm; prism faces are striated parallel to [100] .
Comment:
On synthetic material.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
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CIF File Best | x | y | z | a | b | c
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Rotation
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0000260 | Aksaite | Dal Negro A, Ungaretti L, Sabelli C (1971) The crystal structure of aksaite American Mineralogist 56 1553-1566 |  | 1971 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.36 Å | (100) |
| 4.68 Å | (90) |
| 3.54 Å | (90) |
| 3.19 Å | (90) |
| 6.00 Å | (80) |
| 2.78 Å | (80) |
| 3.09 Å | (70) |
Comments:
Chelkar salt dome, Kazakhstan. Data from the type description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Type Occurrence of Aksaite
General Appearance of Type Material:
Elongated crystals up to 7 mm.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 160056.
Geological Setting of Type Material:
In fine-grained halite in a salt dome.
Associated Minerals at Type Locality:
Other Language Names for Aksaite
Common Associates
Related Minerals - Strunz-mindat Grouping
| 6.FA.10 | Mcallisterite | Mg2[B6O7(OH)6]2 · 9H2O |
| 6.FA.15 | Admontite | MgB6O10 · 7H2O |
| 6.FA.20 | Rivadavite | Na6Mg[B6O7(OH)6]4 · 10H2O |
| 6.FA.25 | Teruggite | Ca4Mg[AsO4]2[B6O7(OH)6]2 · 12H2O |
Other Information
IR Spectrum:
Chelkar salt dome material [cm-1]: 3620, 3560w, 3410sh, 3350, 3310sh, 3215, 3120, 2490w, 1656, 1482, 1431s, 1388s, 1365s, 1344s, 1248s, 1198, 1158, 1121s, 1045, 1028, 1005sh, 957, 902, 856, 816, 735, 690, 637w, 600sh, 532w, 457w.
Notes:
Insoluble in water, readily soluble in HCl.
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 Aksaite
mindat.org URL:
https://www.mindat.org/min-73.html
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Please feel free to link to this page.
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References for Aksaite
Localities for Aksaite
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.
Kazakhstan (TL) | |
| Blazko et al. (1962) +3 other references |
Quick NavTopAbout AksaiteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Chelkar salt dome, Aksai Valley, Terekti District, West Kazakhstan Region, Kazakhstan