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Metastudtite
A valid IMA mineral species
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About Metastudtite
Franz E. Studt
Formula:
UO4 · 2H2O
Colour:
Pale yellow
Lustre:
Silky
Specific Gravity:
4.67 (Calculated)
Crystal System:
Orthorhombic
Name:
Named as a dehydration product of studtite. The root name is for Franz Edward Studt (or Stüdt) (30 November 1873, London, England, UK - 3 July 1953, Holborn, England, UK), geologist for Tanganyika Concessions Ltd. He prepared an important geological map of Katanga, published in 1913.
Unique Identifiers
Mindat ID:
2687
Long-form identifier:
mindat:1:1:2687:7
IMA Classification of Metastudtite
Classification of Metastudtite
4.GA.15
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
G : Uranyl Hydroxides
A : Without additional cations
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
G : Uranyl Hydroxides
A : Without additional cations
5.3.1.2
5 : OXIDES CONTAINING URANIUM OR THORIUM
3 : AXO4·xH2O
5 : OXIDES CONTAINING URANIUM OR THORIUM
3 : AXO4·xH2O
7.16.5
7 : Oxides and Hydroxides
16 : Oxides of U
7 : Oxides and Hydroxides
16 : Oxides of U
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 |
|---|---|---|
| Mstu | 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 Metastudtite
Optical Data of Metastudtite
Type:
Biaxial (+)
RI values:
nα = 1.640(2) nβ = 1.658(2) nγ = 1.760(2)
2V:
Measured: 47° , Calculated: 48°
Max. Birefringence:
δ = 0.120
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.
Dispersion:
r < v moderate
Optical Extinction:
Z = c (direction of elongation).
Pleochroism:
Not Visible
Chemistry of Metastudtite
Mindat Formula:
UO4 · 2H2O
Elements listed:
Crystallography of Metastudtite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pnma
Cell Parameters:
a = 8.411(1) Å, b = 8.744(1) Å, c = 6.505(1) Å
Ratio:
a:b:c = 0.962 : 1 : 0.744
Unit Cell V:
478.39 ų
Z:
2
Morphology:
Fibrous, or as elongated tablets, to 3 mm; in nodules.
Comment:
Data from Rodriguez et al. (2016). Previously assumed to have space group Immm. "In light of the structure determination for studtite, it is likely that the correct unit cell of metastudtite is larger than previously thought, as the repeat length of the chain of uranyl polyhedra in studtite is 8.4 Å, and is not compatible with the 4.2 Å cell dimension" (Burns & Hughes, 2003).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.22 Å | (100) |
| 4.38 Å | (50) |
| 3.79 Å | (50) |
| 3.538 Å | (80) |
| 3.214 Å | (50b) |
| 2.756 Å | (30) |
| 2.669 Å | (20) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 57 : Other minerals formed by human processes |
Type Occurrence of Metastudtite
General Appearance of Type Material:
Aggregates of flexible pale yellow fibers. Also as elongated tablets.
Place of Conservation of Type Material:
Royal Museum of Central Africa, Tervuren, Belgium, RGM13748 and RGM13755.
Geological Setting of Type Material:
Secondary uranium mineral.
Associated Minerals at Type Locality:
Shinkolobwe Mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo