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Sphaerobismoite

A valid IMA mineral species
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About SphaerobismoiteHide

Formula:
Bi2O3
Colour:
Green, pale yellow, gray
Lustre:
Sub-Adamantine
Hardness:
4
Specific Gravity:
7.17 (Calculated)
Crystal System:
Tetragonal
Name:
For the form of the aggregates and the composition.
Dimorph of:
The natural analogue of synthetic β-Bi2O3. A metastable polymorph of bismite.


Unique IdentifiersHide

Mindat ID:
7308
Long-form identifier:
mindat:1:1:7308:6

IMA Classification of SphaerobismoiteHide

Approved
IMA Formula:
Bi3+2O3
Approval year:
1993

Classification of SphaerobismoiteHide

4.CB.65

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
C : Metal: Oxygen = 2: 3,3: 5, and similar
B : With medium-sized cations
4.3.13.1

4 : SIMPLE OXIDES
3 : A2X3

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
SbmIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of SphaerobismoiteHide

Sub-Adamantine
Transparency:
Transparent
Colour:
Green, pale yellow, gray
Comment:
Semitransparent
Streak:
White
Hardness:
Fracture:
Conchoidal
Density:
7.17 g/cm3 (Calculated)

Optical Data of SphaerobismoiteHide

Type:
Uniaxial (+)
RI values:
nω = 2.13 nε = 2.18
Max. Birefringence:
δ = 0.050
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.

Surface Relief:
Very High (positive)
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 uniaxial interference figure - the conoscopic (convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis centred and vertical. The coloured rings are isochromatics, computed with the same physics as the Michel-Lévy bar above; the dark cross is the isogyre.

For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.

Chemistry of SphaerobismoiteHide

Mindat Formula:
Bi2O3
Element Weights:
Element% weight
Bi89.699 %
O10.301 %

Calculated from ideal end-member formula.
Bi
O
Common Impurities:
As

Crystallography of SphaerobismoiteHide

Crystal System:
Tetragonal
Cell Parameters:
a = 8.02(2) Å, c = 6.46(2) Å
Ratio:
a:c = 1 : 0.805
Unit Cell V:
415.51 ų (Calculated from Unit Cell)
Z:
4
Comment:
Space group P42/n or P42212. Synthetic material is reported to have space group P-421c (Blower & Greaves, 1988).

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0010069SphaerobismoiteBlower S K, Greaves C (1988) The structure of beta-Bi2O3 from powder neutron diffraction data Acta Crystallographica C44 587-5891988synthetic0293
0015772SphaerobismoiteGattow G, Schutze D (1964) Uber Wismutoxide. VI. Uber ein Wismut(III)-oxid mit hoherem sauerstoffgehalt (beta-modifikation) Zeitschrift fur Anorganische und Allgemeine Chemie 328 44-681964synthetic0293
0015771SphaerobismoiteGattow G, Schutze D (1964) Uber Wismutoxide. VI. Uber ein Wismut(III)-oxid mit hoherem sauerstoffgehalt (beta-modifikation) Zeitschrift fur Anorganische und Allgemeine Chemie 328 44-681964synthetic0293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
3.16 Å(100)
5.73 Å(70)
1.902 Å(60)
3.44 Å(50)
2.02 Å(50)

Geological EnvironmentHide

Paragenetic Mode(s):