Tengchongite
A valid IMA mineral species
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About Tengchongite
Formula:
Ca(UO2)6(MoO4OH)2O2(OH)4 · 9H2O
formerly given as CaO·6UO3·2MoO3·12H2O
Colour:
Yellow
Lustre:
Vitreous
Hardness:
2 - 2½
Specific Gravity:
4.25
Crystal System:
Orthorhombic
Name:
Named after its discovery locality, Tengchong District, Yunnan Province, China.
Type Locality:
Seems to be the first hydroxymolybdate among the mineral species.
"New type of structural connectivity between U- and Mo-polyhedra for uranyl molybdate minerals."
which are connected by sharing vertices among them, as well as with MoO5 trigonal bipyramids. These sheets, parallel to [010], are linked together by Ca2+ and H2O groups.
The structure is based on sheets that comprise:
* six-membered clusters of edge-sharing UO7 pentagonal bipyramids, that share their vertices,
* MoO5 trigonal bipyramids, that share edges and vertices with the former
The sheets are linked by Ca2+ and H2O.
"New type of structural connectivity between U- and Mo-polyhedra for uranyl molybdate minerals."
which are connected by sharing vertices among them, as well as with MoO5 trigonal bipyramids. These sheets, parallel to [010], are linked together by Ca2+ and H2O groups.
The structure is based on sheets that comprise:
* six-membered clusters of edge-sharing UO7 pentagonal bipyramids, that share their vertices,
* MoO5 trigonal bipyramids, that share edges and vertices with the former
The sheets are linked by Ca2+ and H2O.
Unique Identifiers
Mindat ID:
3909
Long-form identifier:
mindat:1:1:3909:9
IMA Classification of Tengchongite
Approved
IMA Formula:
Ca(U6+O2)6(Mo6+O4OH)2O2(OH)4·9H2O
Approval year:
1984
First published:
1986
Classification of Tengchongite
7.HB.20
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
H : Uranium and uranyl molybdates and wolframates
B : With U6+
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
H : Uranium and uranyl molybdates and wolframates
B : With U6+
49.3.1.2
49 : HYDRATED MOLYBDATES AND TUNGSTATES
3 : Hydrated Molybdates and Tungstates Containing Hydroxyl or Halogen
49 : HYDRATED MOLYBDATES AND TUNGSTATES
3 : Hydrated Molybdates and Tungstates Containing Hydroxyl or Halogen
27.3.12
27 : Sulphites, Chromates, Molybdates and Tungstates
3 : Molybdates
27 : Sulphites, Chromates, Molybdates and Tungstates
3 : Molybdates
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 |
|---|---|---|
| Tcg | 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 Tengchongite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Yellow
Hardness:
2 - 2½ on Mohs scale
Cleavage:
Perfect
{001}
{001}
Density:
4.25(2) g/cm3 (Measured) 4.24 g/cm3 (Calculated)
Optical Data of Tengchongite
Type:
Biaxial (-)
RI values:
nα = 1.663(2) nβ = 1.760(2) nγ = 1.762(2)
2V:
Measured: 16° , Calculated: 16°
Max. Birefringence:
δ = 0.099
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
Dispersion:
weak
Chemistry of Tengchongite
Mindat Formula:
Ca(UO2)6(MoO4OH)2O2(OH)4 · 9H2O
formerly given as CaO·6UO3·2MoO3·12H2O
formerly given as CaO·6UO3·2MoO3·12H2O
Element Weights:
Crystallography of Tengchongite
Crystal System:
Orthorhombic
Class (H-M):
222 - Disphenoidal
Cell Parameters:
a = 13.0866(8) Å, b = 17.6974(12) Å, c = 15.6800(9) Å
Ratio:
a:b:c = 0.739 : 1 : 0.886
Unit Cell V:
3627.8 ų
Z:
4
Comment:
Space Group: C2221
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.84 Å | (100) |
| 3.17 Å | (80) |
| 3.38 Å | (70) |
| 5.37 Å | (50) |
| 4.27 Å | (50) |
| 3.65 Å | (40) |
| 2.04 Å | (40) |
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 Tengchongite
General Appearance of Type Material:
Fine granular crystals.
Place of Conservation of Type Material:
Beijing Uranium Geology Research Institute, Beijing, China.
Associated Minerals at Type Locality:
Synonyms of Tengchongite
Other Language Names for Tengchongite
Related Minerals - Strunz-mindat Grouping
| 7.HB.15 | Calcurmolite | Ca[(UO2)3(MoO4)2(OH)4](H2O)~5.0 |
| 7.HB.25 | Uranotungstite | (Ba0.35Pb0.27)Σ0.62[(U6+O2)2(W6+0.98Fe3+0.26◻0.75)O4.7(OH)2.5(H2O)1.75](H2O)1.67 |
| 7.HB.25 | Wolfsriedite | Pb[(UO2)2(W6+Fe3+)O7(OH)](H2O)3 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 62.7399% | 15,684,975 | 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
Other Information
Notes:
Radioactive
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 Tengchongite
mindat.org URL:
https://www.mindat.org/min-3909.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 Tengchongite
Reference List:
Hawthorne, Frank C., Burke, Ernst A. J., Ercit, T. Scott, Grew, Edward S., Grice, Joel D., Jambor, John L., Puziewicz, Jacek, Roberts, Andrew C., Vanko, David A. (1988) New Mineral Names. American Mineralogist, 73 (1-2) 189-199
Localities for Tengchongite
Showing 3 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.
China (TL) | |
| Chen Zhangru et al. (1986) |
| Chen et al. (1990) +1 other reference |
Russia | |
| M.E. Ciriotti (2005) |
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Oktyabr'skoe Mo-U Deposit, Strel'tsovskoe Mo-U ore field, Krasnokamensk, Krasnokamensky District, Zabaykalsky Krai, Russia