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Mg4(UO2)4(Si2O5)5.5(OH)5 · 13H2O
Light yellow, ...
Vitreous, Silky
2 - 3
The name reflects the URANium and SILicon content
The original publication considered two varieties: calcium ursilite ("almost pure Ca-U-silicate") and magnesium ursilite (("almost pure Mg-U-silicate").
A reinvestigation and crystal-structure study seems necessary.

Classification of Ursilite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates URL:
Please feel free to link to this page.

Type Occurrence of Ursilite

Occurrences of Ursilite

Geological Setting:
Uranium deposit

Physical Properties of Ursilite

Vitreous, Silky
Light yellow, straw-yellow
Hardness (Mohs):
2 - 3
3.25 g/cm3 (Calculated)

Crystallography of Ursilite

Crystal System:
Cell Parameters:
a = 11.60Å, b = 14.68Å, c = 12.83Å
a:b:c = 0.79 : 1 : 0.874
Unit Cell Volume:
V 2,184.80 ų (Calculated from Unit Cell)
Needlelike crystals (only visible in SEM)

Optical Data of Ursilite

Biaxial (-)
RI values:
nα = 1.570 nγ = 1.584
Max Birefringence:
δ = 0.014
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:

Chemical Properties of Ursilite

Mg4(UO2)4(Si2O5)5.5(OH)5 · 13H2O
All elements listed in formula:

Relationship of Ursilite to other Species

9.AK.05Soddyite(UO2)2SiO4 · 2H2O
9.AK.10CuprosklodowskiteCu(UO2)2(SiO3OH]2 · 6H2O
9.AK.10OursiniteCo(UO2)2(SiO3OH)2 · 6H2O
9.AK.10SklodowskiteMg(UO2)2(SiO3OH)2 · 6H2O
9.AK.15Boltwoodite(K,Na)(UO2)(SiO3OH] · 1.5H2O
9.AK.15KasolitePb(UO2)[SiO4] · H2O
9.AK.15NatroboltwooditeNa(UO2)(SiO3OH) · H2O
9.AK.15Uranophane-βCa(UO2)2(HSiO4)2 · 5H2O
9.AK.15UranophaneCa(UO2)2[HSiO4]2 · 5H2O
9.AK.20SwamboiteU6+(UO2)6(SiO3OH)6 · 30H2O
9.AK.25HaiweeiteCa(UO2)2[Si5O12(OH)2] · 6H2O
9.AK.25MetahaiweeiteCa(UO2)2Si6O15 · nH2O
9.AK.30WeeksiteK2(UO2)2(Si5O13) · 4H2O
9.AK.30CoutinhoiteThxBa(1-2x)(UO2)2Si5O13 · (H2O)1+y (0 < x < 0.5 and 0 < y < (2+x))
9.AK.35MagnioursiliteMg4(UO2)4(Si2O5)5(OH)6 · 20H2O
9.AK.35CalcioursiliteCa4(UO2)4(Si2O5)5(OH)6 · 15H2O
9.AK.40UranosiliteUO3 · 7SiO2

Other Names for Ursilite

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Ursilite

Reference List:
Chernikov 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.

Chernikov 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).

Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva (1977): 106: 553-564.

Internet Links for Ursilite

Localities for Ursilite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
  • Helmand Province (Hilmend Province; Hilmand Province)
    • Dushan District
      • Khanneshin complex
Orris, G.J., and Bliss, J.D. (2002): Mines and Mineral Occurrences of Afghanistan. United States Geological Survey Open-File Report 02-110
  • Region of Republican Subordination
    • Tien Shan Mtn
      • Alai Range (Alayskiy)
  • Viloyati Sogd (Viloyati Sughd; Viloyati Khodzhent; Viloyati Leninabad)
    • Khodzhent (Leninabad)
      • Kyzyltyube-Sai
Pekov, I. (1998) Minerals First discovered on the territory of the former Soviet Union 369p. Ocean Pictures, Moscow
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