Calcioursilite

Ca4(UO2)4(Si2O5)5(OH)6 · 15H2O
IMA status
  • Approved
  • Grandfathered
IMA symbol
Caur
Also known as
  • Ca-ursilit
  • Calcioursiliet
  • Calcium-ursilite

Where it forms, where it's found

Geological setting

Forms in granite-porphyry.

Type locality
Oktyabr'skoye U Deposit
  1. Kyzyltyube-Sai
  2. Khodzhent (Leninabad)
  3. Sughd
  4. Tajikistan
1recorded occurrences
Source · OpenStreetMap

Radioactivity

Physical

Colour
Lemon yellow

Optical

Pleochroism
Weak

X = pale green, Z = green.

Extinction
Parallel.
UV response
Distinctly fluorescent in greenish yellow under ultraviolet light.
Notes

Interference colors are gray in thin-sections of normal thickness. The indices of refraction are very near each other.

Crystallography

Crystal system
Orthorhombic
Cell parameters
a = 14.09(6) Å · b = 17.87(1) Å · c = 18.24 Å
Ratio a:b:c
1 : 1.268 : 1.295
Type-locality form

Forms acicular crystals, spherulites and earthy masses.

Comment

Poorly defined crystallography

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
92UUraniumUranium4238.029952.116
41.51%
8OOxygenOxygen5415.999863.946
37.67%
14SiSiliconSilicon1028.085280.850
12.25%
20CaCalciumCalcium440.078160.312
6.99%
1HHydrogenHydrogen361.00836.288
1.58%
Total2293.512100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • Ca-ursilit
  • Calcioursiliet
  • Calcium-ursilite

In other languages

German
Calcioursilit
Spanish
Calcioursilita
Italian
calcioursilite

Classification

Strunz
10th ed.

9.AK.35

  • 9SilicatesClass
  • 9.ANesosilicatesDivision
  • 9.AKUranyl neso- and polysilicatesGroup
  • 9.AK.35CalcioursiliteSpecies

Literature, links & citation

Citations
  1. 1957Chernikov A A, Krumetskaia O V, Sidel'nikova V D (1957): Ursilite - a new silicate of uranium. Atomnaya Energiya Voprosy Geologii Urana, Supplement 6, 61-65.
  2. 1957Chernikov A A, Krutetskaya O V, Sidelnikova V D (1957): Ursilite - a new silicate of uranium. Atomnaya Energiya Voprosy Geologii Urana, Supplement 6, 73-77 (in Russian).
  3. 1977Chernikov, A.A., Sidorenko, G.A., Valueva, A.A. (1977): New data on uranyl minerals of the ursilite-weeksite group. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva 106 (5), 553-564 (in Russian).
  4. 2018Plášil, Jakub (2018) Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates. Minerals, 8 (12) 551 doi:10.3390/min8120551DOI: 10.3390/min8120551
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Calcioursilite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/calcioursilite-11360},
  note      = {Accessed 2026-05-11}
}