SUPPORT US. Covid-19 has significantly affected our fundraising. Please help!
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice SettingsThe Mineral Quiz
Photo SearchPhoto GalleriesSearch by ColorNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography


This page is currently not sponsored. Click here to sponsor this page.
Hide all sections | Show all sections

About SidwilliteHide

Sidney A. Williams
MoO3 · 2H2O
Specific Gravity:
Crystal System:
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.
This page provides mineralogical data about Sidwillite.

Classification of SidwilliteHide

Approval year:
First published:

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

5 : AX3

7 : Oxides and Hydroxides
15 : Oxides of Mo and W

Physical Properties of SidwilliteHide

(Cesbron and Ginderow 1985)
pleochroic, colorless - yellow at 47° ^ a-axis (Cesbron and Ginderow 1985)
2½ on Mohs scale
[010] (Cesbron and Ginderow 1985)
3.12 g/cm3 (Measured)    3.11 g/cm3 (Calculated)
Data from Cesbron and Ginderow 1985

Optical Data of SidwilliteHide

Biaxial (-)
RI values:
nα = 1.700 nβ = 2.210 nγ = 2.380
Measured: 48° , Calculated: 48°
Max Birefringence:
δ = 0.680
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
relatively weak

Chemical Properties of SidwilliteHide

MoO3 · 2H2O

Crystallography of SidwilliteHide

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

Crystal StructureHide

Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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
CIF File    Best | x | y | z | a | b | c
Stop | Start
Console Off | On | Grey | Yellow
IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0009439SidwilliteKrebs B (1972) Die kristallstruktur von MoO3*2H2O Acta Crystallographica B28 2222-22311972synthetic0293
0020017SidwilliteCesbron F, Ginderow D (1985) La sidwillite, MoO3*2H2O; une nouvelle espece minerale de Lake Como, Colorado, U.S.A. Bulletin de Mineralogie 108 813-8231985Lake Como, Colorado, USA0293
CIF Raw Data - click here to close

Type Occurrence of SidwilliteHide

Place of Conservation of Type Material:
Collection de Mineralogie de I'Ecole nationale superieure
des Mines de Paris.
Geological Setting of Type Material:
quartz vein
Associated Minerals at Type Locality:
Cesbron, F., Ginderow, D. (1985) Sidwillite MoO3·2H2O; a new mineral species from Lake Como, Colorado, U.S.A. Bulletin de la Société française de Minéralogie et de Cristallographie 108: 813-823.

Synonyms of SidwilliteHide

Other Language Names for SidwilliteHide

Simplified Chinese:黄钼矿

Related Minerals - Nickel-Strunz GroupingHide

4.FJ.05MeymaciteWO3 · 2H2OAmor.
4.FJ.10TungstiteWO3 · H2OOrth.
4.FJ.15HydrotungstiteWO3 · 2H2OMon.
4.FJ.15IlsemanniteMo3O8 · nH2O

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

7.15.1TugarinoviteMoO2Mon. 2/m : P21/b
7.15.2MolybditeMoO3Orth. mmm (2/m 2/m 2/m) : Pbcm
7.15.4IlsemanniteMo3O8 · nH2O
7.15.5TungstiteWO3 · H2OOrth.
7.15.6HydrotungstiteWO3 · 2H2OMon.
7.15.7MeymaciteWO3 · 2H2OAmor.
7.15.8Alumotungstite2W2O6(H2O)Iso. m3m (4/m 3 2/m) : Fd3m
7.15.9JixianitePb(W,Fe3+)2(O,OH)7Iso. m3m (4/m 3 2/m) : Fd3m

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.

References for SidwilliteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Lindqvist, I. (1950) The crystal structure of the yellow molybdic acid, MoO3·2H2O. Acta Chemica Scandinavica: 4: 650-657.
Krebs, B. (1972) Die kristallstruktur von MoO3·2H2O. Acta Crystallographica: B28: 2222-2231.
Cesbron, F., Ginderow, D. (1985) Sidwillite MoO3·2H2O; a new mineral species from Lake Como, Colorado, U.S.A. Bulletin de la Société française de Minéralogie et de Cristallographie 108: 813-823.
Grice J.D. (1986) New mineral names - sidwillite. American Mineralogist: 71: 1546.

Internet Links for SidwilliteHide

Localities for SidwilliteHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Colorado
    • San Juan Co.
"Minerals of Colorado, updated & revised", p. 437, by Eckel, Edwin B., 1997
  • New Mexico
    • Luna Co.
      • Cookes Peak Mining District
Ramon S. DeMark; Dr. Virgil W Lueth; Abstract, "A New Mexico Occurrence of sidwillite and other molybdenum minerals", 37th Annual New Mexico Mineral Symposium
  • Utah
    • Piute Co.
      • Marysvale Mining District (Marysvale Uranium area)
Collected by and in the collection of Brent Thorne. SEM EDS and XRD analyzed by Andy Roberts.
Mineral and/or Locality  
Mindat Discussions Facebook Logo Instagram Logo Discord Logo is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © and the Hudson Institute of Mineralogy 1993-2021, except where stated. Most political location boundaries are © OpenStreetMap contributors. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us - Report a bug/vulnerability Current server date and time: April 13, 2021 20:19:01 Page generated: March 17, 2021 20:22:10
Go to top of page