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Sidwillite
A valid IMA mineral species
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About Sidwillite
Sidney A. Williams
Formula:
MoO3 · 2H2O
Colour:
Canary-yellow
Lustre:
Resinous
Hardness:
2½
Specific Gravity:
3.12
Crystal System:
Monoclinic
Name:
Named in 1985 by Fabian Cesbron and Daria Ginderow in honor of Sidney Arthur Williams [December 26, 1933 Ann Arbor, Michigan, USA - December 8, 2006 Douglas, Arizona, USA], mineralogist, Phelps Dodge Corporation, Douglas, Arizona, USA. Sid Williams had a profound interest in systematic mineralogy and systematic language. His choice of using native languages of the region from where he named a mineral is unmatched in mineralogy.
Type Locality:
Higher-hydrate counterpart of raydemarkite (monohydrate), tianhuixinite (1/3-hydrate), and molybdite (anhydrous).
Unique Identifiers
Mindat ID:
3654
Long-form identifier:
mindat:1:1:3654:8
IMA Classification of Sidwillite
Approved
IMA Formula:
Mo6+O3·2H2O
Approval year:
1983
First published:
1985
Classification of Sidwillite
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
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
4.5.6.1
4 : SIMPLE OXIDES
5 : AX3
4 : SIMPLE OXIDES
5 : AX3
7.15.3
7 : Oxides and Hydroxides
15 : Oxides of Mo and W
7 : Oxides and Hydroxides
15 : Oxides of Mo and W
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Sdw | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Sidwillite
Resinous
Transparency:
Translucent
Comment:
(Cesbron and Ginderow 1985)
Colour:
Canary-yellow
Comment:
pleochroic, colorless - yellow at 47° ^ a-axis (Cesbron and Ginderow 1985)
Streak:
Pale yellow
Hardness:
2½ on Mohs scale
Cleavage:
Perfect
[010] (Cesbron and Ginderow 1985)
[010] (Cesbron and Ginderow 1985)
Density:
3.12 g/cm3 (Measured) 3.11 g/cm3 (Calculated)
Comment:
Data from Cesbron and Ginderow 1985
Optical Data of Sidwillite
Type:
Biaxial (-)
RI values:
nα = 1.70(1) nβ = 2.21(2) nγ = 2.38(2)
2V:
Measured: 48° , Calculated: 48°
Max. Birefringence:
δ = 0.680
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
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.
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.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
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.
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.
Dispersion:
relatively weak
Pleochroism:
Strong
Comments:
X = colorless; Y = Z = yellow.
Chemistry of Sidwillite
Mindat Formula:
MoO3 · 2H2O
Elements listed:
Crystallography of Sidwillite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Setting:
P21/n
Cell Parameters:
a = 10.618(5) Å, b = 13.825(7) Å, c = 10.482(5) Å
β = 91.61(4)°
β = 91.61(4)°
Ratio:
a:b:c = 0.768 : 1 : 0.758
Unit Cell V:
1,538.09 ų (Calculated from Unit Cell)
Z:
16
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0020017 | Sidwillite | Cesbron F, Ginderow D (1985) La sidwillite, MoO3*2H2O; une nouvelle espece minerale de Lake Como, Colorado, U.S.A. Bulletin de Mineralogie 108 813-823 | 1985 | Lake Como, Colorado, USA | 0 | 293 | |
| 0009439 | Sidwillite | Krebs B (1972) Die kristallstruktur von MoO3*2H2O Acta Crystallographica B28 2222-2231 |  | 1972 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.322 Å | (100) |
| 3.248 Å | (93) |
| 6.94 Å | (84) |
| 3.680 Å | (58) |
| 3.79 Å | (53) |
| 2.656 Å | (51) |
| 2.620 Å | (41) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] |
Type Occurrence of Sidwillite
Place of Conservation of Type Material:
Collection de Mineralogie de I'Ecole nationale superieure
des Mines de Paris.
des Mines de Paris.
Geological Setting of Type Material:
quartz vein
Associated Minerals at Type Locality:
Synonyms of Sidwillite
Other Language Names for Sidwillite
Common Associates
Associations Based on Photo Data:
| 11 photos of Sidwillite associated with Raydemarkite | MoO3 · H2O |
| 3 photos of Sidwillite associated with Ilsemannite | Mo3O8 · nH2O |
| 2 photos of Sidwillite associated with Baryte | BaSO4 |
| 1 photo of Sidwillite associated with Molybdite | MoO3 |
| 1 photo of Sidwillite associated with Jordisite | MoS2 |
| 1 photo of Sidwillite associated with Quartz | SiO2 |
| 1 photo of Sidwillite associated with Stunorthropite | (NH4)4[Mo2O6(MoO4)2] |
Related Minerals - Strunz-mindat Grouping
| 4.FJ. | Raydemarkite | MoO3 · H2O |
| 4.FJ.05 | Meymacite | WO3 · 2H2O |
| 4.FJ.10 | Tungstite | WO3 · H2O |
| 4.FJ.15 | Hydrotungstite | WO3 · 2H2O |
| 4.FJ.15 | Ilsemannite | Mo3O8 · nH2O |
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.
Internet Links for Sidwillite
mindat.org URL:
https://www.mindat.org/min-3654.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Sidwillite
Reference List:
Lindqvist, Ingvar, Hassel, O., Sillén, Lars Gunnar, Rottenberg, Max (1950) The Crystal Structure of the Yellow Molybdic Acid, MoO3.2H2O. On the Existence of an H4O2+ Ion. Acta Chemica Scandinavica, 4. 650-657 doi:10.3891/acta.chem.scand.04-0650
Krebs, B. (1972) Die Kristallstruktur von MoO3.2H2O. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 28 (7) 2222-2231 doi:10.1107/s0567740872005849
Cesbron, Fabien, Ginderow, Daria (1985) La sidwillite, MoO3·2H2O ; une nouvelle espèce minérale de Lake Como, Colorado, U.S.A. Bulletin de Minéralogie, 108 (6) 813-823 doi:10.3406/bulmi.1985.7899
Hawthorne, F.C., Bladh, K.W., Burke, E.A.J., Ercit, S., Grew, E.S., Grice, J.D., Puziewicz, J., Roberts, A.C., Schedler, R.A., Shigley, J.E. (1986) New mineral names. American Mineralogist: 71: 1543-1548.pp.1545-1546 - (p. 1546: Sidwillite and Ungursaite)
Localities for Sidwillite
Showing 3 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
USA (TL) | |
| Cesbron et al. (1985) +1 other reference |
| Ramon S. DeMark +4 other references |
| Collected by and in the collection of ... |
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Cookes Peak Mining District, Luna County, New Mexico, USA