Ursilite
About Ursilite
Historically, calcioursilite and magnioursilite were described together in 1957 as “ursilite” from the Oktyabr’skoye deposit, Kyzyltyube-Saj, Samgar Steppe, Tajikistan. The original publication considered two varieties: calcium ursilite ("almost pure Ca-U-silicate") and magnesium ursilite ("almost pure Mg-U-silicate").
The analyses showed Ca >Mg and Mg > Ca. Subsequently, calcioursilite and magnioursilite were defined instead of ursilite, and “ursilite” was officially discredited in 2018.
Unique Identifiers
Similar Names
| Ureilite | A synonym of 'Ureilite meteorite' |
IMA Classification of Ursilite
Discredited by IMA in April 2018, executive decision taken by the officers of the IMA CNMNC.
Classification of Ursilite
9 : SILICATES (Germanates)
:
:
Physical Properties of Ursilite
Optical Data of Ursilite
Based on recorded range of RI values above.
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.
Relative to Canada balsam mounting medium (n ≈ 1.537).
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.
No measured or calculated 2V is on file for this mineral, so the value used here (90°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Chemistry of Ursilite
Crystallography of Ursilite
Geological Environment
First Recorded Occurrence of Ursilite
Synonyms of Ursilite
Other Language Names for Ursilite
Ursilit
Common Associates
Related Minerals - Strunz-mindat Grouping
Radioactivity
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 39.5758% | 9,893,950 | 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.
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
Internet Links for Ursilite
Please feel free to link to this page.
Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan