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Sidwillite

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Freedom No. 2 Mine, Marysvale District (Marysvale Uranium area), Piute Co., Utah, USA
© Brent Thorne

Show Sidwillite Photos (3)
Formula:
MoO
 
3
·2H
 
2
O
System:MonoclinicColour:Canary-yellow
Hardness:2½
Name:Named after Dr. Sidney A. Williams, mineralogist, Phelps Dodge Corporation, Douglas, Arizona, USA.
This page provides mineralogical data about Sidwillite.

Classification of Sidwillite

IMA status:Approved 1983
Strunz 8th edition ID:4/E.03-20
Nickel-Strunz 10th (pending) edition ID:4.FJ.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
J : Hydroxides with H2O +- (OH); corner-sharing octahedra
Dana 8th edition ID:4.5.6.1

4 : SIMPLE OXIDES
5 : AX3
Hey's CIM Ref.:7.15.3

7 : Oxides and Hydroxides
15 : Oxides of Mo and W
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Type Occurrence of Sidwillite

Type Locality:Lake Como, San Juan Co., Colorado, USA
Year of Discovery:1985

Physical Properties of Sidwillite

Lustre:Adamantine, Waxy
Colour:Canary-yellow
Hardness (Mohs):2½

Crystallography of Sidwillite

Crystal System:Monoclinic
Cell Parameters:a = 10.61Å, b = 13.82Å, c = 10.48Å
β = 91.61°
Ratio:a:b:c = 0.768 : 1 : 0.758
Unit Cell Volume:V 1,536.08 ų (Calculated from Unit Cell)

Optical Data of Sidwillite

Type:Biaxial (-)
RI values: nα = 1.700 nβ = 2.210 nγ = 2.380
2V:Measured: 48° , Calculated: 48°
Maximum Birefringence:δ = 0.680

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High
Dispersion:relatively weak

Chemical Properties of Sidwillite

Formula:
MoO
 
3
·2H
 
2
O
Essential elements:H, Mo, O
All elements listed in formula:H, Mo, O

Relationship of Sidwillite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
4.FJ.05Meymacite
WO
 
3
·2H
 
2
O
4.FJ.10Tungstite
WO
 
3
·H
 
2
O
4.FJ.15Hydrotungstite
WO
 
3
·2H
 
2
O
4.FJ.15Ilsemannite
Mo
 
3
O
 
8
·nH
 
2
O
4.FJ.20Parabariomicrolite
BaTa
 
4
O
 
10
(OH)
 
2
·2H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
7.15.1Tugarinovite
MoO
 
2
7.15.2Molybdite
MoO
 
3
7.15.4Ilsemannite
Mo
 
3
O
 
8
·nH
 
2
O
7.15.5Tungstite
WO
 
3
·H
 
2
O
7.15.6Hydrotungstite
WO
 
3
·2H
 
2
O
7.15.7Meymacite
WO
 
3
·2H
 
2
O
7.15.8Alumotungstite
(W,Al)(O,OH)
 
3
7.15.9Jixianite
Pb(W,Fe
3+
 
)
 
2
(O,OH)
 
7

Other Names for Sidwillite

Synonyms:
IMA1983-089
Other Languages:
German:Sidwillit
Russian:Сидвиллит
Spanish:Sidwillita

Other Information

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

References for Sidwillite

Reference List:Bulletin de la Société française de Minéralogie et de Cristallographie (1985): 108: 813-823.

American Mineralogist (1986): 71: 1546.

Articles/Blogs about Sidwillite

Internet Links for Sidwillite

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  • Raman and XRD data at RRUFF project
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    Localities for Sidwillite

    (TL) indicates type locality. ? 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.
    USA
     
    • Colorado
      • San Juan Co.
    		"Minerals of Colorado, updated & revised", p. 437, by Eckel, Edwin B., 1997
    • Utah
      • Piute Co.
        • Marysvale District (Marysvale Uranium area)
    Mineral and/or Locality
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