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Downeyite

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Formula:
SeO2
System:
Tetragonal
Colour:
Colourless (red - ...
Lustre:
Adamantine
Name:
For Wayne F. Downey, Jr., who discovered the mineral. He was a high school student at the time.
Naturally occuring selenium(IV) oxide, extremely hygroscopic.

Classification of Downeyite

Approved 1974
4.DE.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
E : With medium-sized cations; with various polyhedra
4.4.3.1

4 : SIMPLE OXIDES
4 : AX2
7.17.1

7 : Oxides and Hydroxides
17 : Oxides of Se and Te
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First Recorded Occurrence of Downeyite

General Appearance of First Recorded Material:
Acicular to prismatic crystals
Place of Conservation of First Recorded Material:
Smithsonian
Year of Discovery:
1971
Geological Setting of First Recorded Material:
Burning anthracite culm banks

Occurrences of Downeyite

Geological Setting:
Burning coal banks.

Physical Properties of Downeyite

Adamantine
Diaphaneity (Transparency):
Transparent
Colour:
Colourless (red - included selenium, yelllow - included sulfur)
Density:
4.146 g/cm3 (Calculated)

Crystallography of Downeyite

Crystal System:
Tetragonal
Cell Parameters:
a = 8.36Å, c = 5.06Å
Ratio:
a:c = 1 : 0.605
Unit Cell Volume:
V 353.64 ų (Calculated from Unit Cell)
Morphology:
Acicular crystals to 2 cm.

Optical Data of Downeyite

Type:
Uniaxial (+)
Comments:
Extremely hygroscopic. In air will deliquesce in a few minutes and be absorbed into substrate or evaporate leaving colorless film.

Chemical Properties of Downeyite

Formula:
SeO2
Essential elements:
All elements listed in formula:

Relationship of Downeyite to other Species

4.DE.10Koragoite(Mn2+,Fe3+)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20
4.DE.15KoechliniteBi2MoO6
4.DE.15RusselliteBi2WO6
4.DE.15TungstibiteSb23+WO6
4.DE.20TelluriteTeO2
4.DE.25ParatelluriteTeO2
4.DE.30BismutotantaliteBi(Ta,Nb)O4
4.DE.30BismutocolumbiteBi(Nb,Ta)O4
4.DE.30CervantiteSb3+Sb5+O4
4.DE.30StibiotantaliteSb(Ta,Nb)O4
4.DE.30StibiocolumbiteSb(Nb,Ta)O4
4.DE.30ClinocervantiteSb3+Sb5+O4
4.DE.35BaddeleyiteZrO2

Other Names for Downeyite

Name in Other Languages:
German:Downeyit
Spanish:Downeyita

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 Downeyite

Reference List:
Finkelman, R. B. & Mrose, M. E. (1977): Downeyite, the first verified natural occurrence of selenium dioxide. American Mineralogist 62, 316-320.

Journal of the American Chemical Society: 59: 789-794.

Internet Links for Downeyite

Localities for Downeyite

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.
USA
 
  • Pennsylvania
    • Northumberland Co.
Mineralogy associated with burning Anthracite deposits of Eastern Pennsylvania, D. M. Lapham, J. H. Barns, W. Downey Jr. and R. B. Finkelman, Min. Rescs. Report #78, 1980
    • Schuylkill Co.
Finkelman, R.B. & Mrose, M.E. (1977) American Mineralogist: 62,316-320.
Mineral and/or Locality  
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