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Ursilite

A synonym
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About UrsiliteHide

Formula:
(Mg/Ca)4(UO2)4(Si2O5)5.5(OH)5 · 13H2O
Lustre:
Vitreous, Silky
Hardness:
2 - 3
Specific Gravity:
3.25 (Calculated)
Crystal System:
Orthorhombic
Name:
The name reflects the URANium and SILicon content.
"Ursilite" is now said to be an obsolete name. The correct minerals names are calcioursilite and magnioursilite.
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 IdentifiersHide

Mindat ID:
4119
Long-form identifier:
mindat:1:1:4119:1
GUID
(UUID V4):
71438db9-05a6-47b5-a42e-28e16d2816db

IMA Classification of UrsiliteHide

Discredited
IMA Formula:
Mg4(UO2)2(Si2O5)5.5(OH)5 · 13H2O
Approval history:
Pre-2018: Status grandfathered.
Discredited by IMA in April 2018, executive decision taken by the officers of the IMA CNMNC.

Classification of UrsiliteHide

9..

9 : SILICATES (Germanates)
:
:

Physical Properties of UrsiliteHide

Vitreous, Silky
Hardness:
2 - 3 on Mohs scale
Density:
3.25 g/cm3 (Calculated)

Optical Data of UrsiliteHide

Type:
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:
Moderate

Chemistry of UrsiliteHide

Mindat Formula:
(Mg/Ca)4(UO2)4(Si2O5)5.5(OH)5 · 13H2O

Crystallography of UrsiliteHide

Crystal System:
Orthorhombic
Cell Parameters:
a = 11.60 Å, b = 14.68 Å, c = 12.83 Å
Ratio:
a:b:c = 0.79 : 1 : 0.874
Unit Cell V:
2,184.80 ų (Calculated from Unit Cell)
Z:
6
Morphology:
Needlelike crystals (only visible in SEM)

Geological EnvironmentHide

Geological Setting:
Uranium deposit

First Recorded Occurrence of UrsiliteHide

Synonyms of UrsiliteHide

Other Language Names for UrsiliteHide

Common AssociatesHide

Associated Minerals Based on Photo Data:
2 photos of Ursilite associated with Arapovite(K1-xx)(Ca,Na)2U4+Si8O20 (x ~ 0.5)

Related Minerals - Strunz-mindat GroupingHide

9..ChrysotileMg3(Si2O5)(OH)4Mon. m : Bb
9..Hiortdahlite INa4Ca8Zr2(Nb,Mn,Ti,Fe,Mg,Al)2(Si2O7)4O3F5Tric. 1 : P1
9..Halloysite-7AMon. m : Bb
9..Afanasyevaite
9..SodicpedriziteMon. 2/m : B2/m
9..Sodic-ferropedrizite

Other InformationHide

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 UrsiliteHide

References for UrsiliteHide

 
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