Baumoite
A valid IMA mineral species
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About Baumoite
Formula:
BaU3Mo2O16(H2O)6
Colour:
Yellow to orange yellow
Lustre:
Vitreous
Hardness:
2½
Specific Gravity:
4.61 (Calculated)
Crystal System:
Monoclinic
Name:
Named for the composition that includes Ba, U, and Mo (barium, uranium and molybdenum).
New structure type. Unique combination of elements.
Typical features of the structure are twinning and incommensurate modulation. The structure is based on sheets of U6+ and Mo6+-bearing polyhedra, the topology of which is unique. Ba atoms are located in partially occupied sites in the interlayer space, where also water molecules occur.
Typical features of the structure are twinning and incommensurate modulation. The structure is based on sheets of U6+ and Mo6+-bearing polyhedra, the topology of which is unique. Ba atoms are located in partially occupied sites in the interlayer space, where also water molecules occur.
Unique Identifiers
Mindat ID:
52162
Long-form identifier:
mindat:1:1:52162:4
Similar Names
IMA Classification of Baumoite
Approved
IMA Formula:
Ba0.5[(U6+O2)3O8Mo6+2(OH)3](H2O)3
Approval year:
2017
First published:
2019
Classification of Baumoite
7.G0.
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
G : Molybdates, Wolframates and Niobates
0 :
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
G : Molybdates, Wolframates and Niobates
0 :
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 |
|---|---|---|
| Bam | 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 Baumoite
Vitreous
Transparency:
Translucent
Colour:
Yellow to orange yellow
Streak:
Pale yellow
Hardness:
2½ on Mohs scale
Comment:
close to
Tenacity:
Brittle
Cleavage:
Perfect
one direction
one direction
Fracture:
Irregular/Uneven
Density:
4.61 g/cm3 (Calculated)
Comment:
4.61 g/cm3 from the empirical formula and 4.68 g/cm3 from the ideal formula
Optical Data of Baumoite
Type:
Biaxial (-)
RI values:
nα = 1.716(4) nβ = 1.761(4) nγ = 1.767(4)
2V:
Calculated: 42.2°
Max. Birefringence:
δ = 0.051
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:
Very High (positive)
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.
Chemistry of Baumoite
Mindat Formula:
BaU3Mo2O16(H2O)6
Element Weights:
Crystallography of Baumoite
Crystal System:
Monoclinic
Cell Parameters:
a = 9.8337(3) Å, b = 15.0436(5) Å, c = 14.2055(6) Å
β = 108.978(4)°
β = 108.978(4)°
Ratio:
a:b:c = 0.654 : 1 : 0.944
Unit Cell V:
1987.25 ų
Z:
4
Comment:
Superspace Group: X2/m(α0γ)0 s with X = (0,½,0,½)
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.175 Å | (39) |
| 7.450 Å | (100) |
| 3.554 Å | (20) |
| 3.365 Å | (31) |
| 3.255 Å | (31) |
| 3.209 Å | (28) |
| 3.067 Å | (33) |
| 2.977 Å | (20) |
Locality:
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Baumoite
General Appearance of Type Material:
thin crusts of tabular to prismatic crystals
Place of Conservation of Type Material:
Cotype material is deposited in mineralogical collections of the South Australian Museum, North Terrace, Adelaide, South Australia, Australia, registration number G34697
Geological Setting of Type Material:
granite matrix
Associated Minerals at Type Locality:
Synonyms of Baumoite
Other Language Names for Baumoite
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 50.7374% | 12,684,350 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 0.0000% | 0 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Baumoite
Bright yellow green under SW UV
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 Baumoite
mindat.org URL:
https://www.mindat.org/min-52162.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Baumoite
Reference List:
Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2017) New minerals and nomenclature modifications approved in 2017, CNMNC Newsletter No 39. Mineralogical Magazine, 81 (5) 1279-1286 doi:10.1180/minmag.2017.081.072
Localities for Baumoite
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.
Australia (TL) | |
| Hålenius et al. (2017) +1 other reference |
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Baumoite type locality, Radium Hill area, Pastoral Unincorporated Area, South Australia, Australia