Downeyite
A valid IMA mineral species
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About Downeyite
Formula:
SeO2
Colour:
Colourless (red - included selenium, yellow - included sulfur)
Lustre:
Adamantine
Specific Gravity:
4.146 (Calculated)
Crystal System:
Tetragonal
Name:
For Wayne F. Downey, Jr. (Harrisburg, Pennsylvania, USA), who discovered the mineral. He was a high school student at the time and devised a way to collect the extremely hygroscopic mineral.
Naturally occuring selenium(IV) oxide, extremely hygroscopic.
Unique Identifiers
Mindat ID:
1315
Long-form identifier:
mindat:1:1:1315:0
IMA Classification of Downeyite
Approved
Approval year:
1974
First published:
1977
Classification of Downeyite
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 : 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
4 : SIMPLE OXIDES
4 : AX2
7.17.1
7 : Oxides and Hydroxides
17 : Oxides of Se and Te
7 : Oxides and Hydroxides
17 : Oxides of Se and Te
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 |
|---|---|---|
| Dny | 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 Downeyite
Adamantine
Transparency:
Transparent
Colour:
Colourless (red - included selenium, yellow - included sulfur)
Streak:
White
Density:
4.146 g/cm3 (Calculated)
Optical Data of Downeyite
Type:
Uniaxial (+)
Optical Extinction:
Parallel
Comments:
Indices of refraction are > 1.80
Chemistry of Downeyite
Mindat Formula:
SeO2
Elements listed:
Crystallography of Downeyite
Crystal System:
Tetragonal
Class (H-M):
4/mmm (4/m 2/m 2/m) - Ditetragonal Dipyramidal
Space Group:
P42/mbc
Setting:
P42/mbc
Cell Parameters:
a = 8.36 Å, c = 5.06 Å
Ratio:
a:c = 1 : 0.605
Unit Cell V:
353.64 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Acicular crystals to 2 cm.
Twinning:
Contact twinning
Crystal Structure
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2x2x2 | 3x3x3 | 4x4x4
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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) |
|---|---|---|---|---|---|---|---|
| 0011027 | Downeyite | Stahl K, Legros J P, Galy J (1992) The crystal structure of SeO2 at 139 and 286 K Zeitschrift fur Kristallographie 202 99-107 |  | 1992 | synthetic | 0 | 139 |
| 0011028 | Downeyite | Stahl K, Legros J P, Galy J (1992) The crystal structure of SeO2 at 139 and 286 K Zeitschrift fur Kristallographie 202 99-107 | | 1992 | synthetic | 0 | 286 |
| 0017909 | Downeyite | McCullough J (1937) The Crystal Structure of Selenium Dioxide _cod_database_code 1010994 Journal of the American Chemical Society 59 789-794 | 1937 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.008 Å | (100) |
| 3.742 Å | (60) |
| 4.180 Å | (55) |
| 3.227 Å | (55) |
| 2.531 Å | (25) |
| 1.933 Å | (18) |
| 1.883 Å | (14) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Geological Setting:
Burning coal banks.
Type Occurrence of Downeyite
General Appearance of Type Material:
Acicular to prismatic crystals
Place of Conservation of Type Material:
National Museum of Natural History (Smithsonian), Washington, D.C, USA
Geological Setting of Type Material:
Burning anthracite culm banks
Associated Minerals at Type Locality:
Synonyms of Downeyite
Other Language Names for Downeyite
Related Minerals - Strunz-mindat Grouping
| 4.DE. | Colchesterite | Bi3+2Mo6+2O9 |
| 4.DE. | Pertoldite | GeO2 |
| 4.DE. | Ziroite | ZrO2 |
| 4.DE.10 | Koragoite | (Mn2+,Fe3+)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20 |
| 4.DE.15 | Russellite | Bi2WO6 |
| 4.DE.15 | Koechlinite | Bi2MoO6 |
| 4.DE.15 | Tungstibite | Sb3+2WO6 |
| 4.DE.20 | Tellurite | TeO2 |
| 4.DE.25 | Paratellurite | TeO2 |
| 4.DE.30 | Bismutotantalite | BiTaO4 |
| 4.DE.30 | Stibiotantalite | Sb(Ta,Nb)O4 |
| 4.DE.30 | Cervantite | Sb3+Sb5+O4 |
| 4.DE.30 | Bismutocolumbite | Bi(Nb,Ta)O4 |
| 4.DE.30 | Stibiocolumbite | Sb(Nb,Ta)O4 |
| 4.DE.30 | Clinocervantite | Sb3+Sb5+O4 |
| 4.DE.35 | Baddeleyite | ZrO2 |
| 4.DE.40 | Billwiseite | Sb3+5Nb3WO18 |
| 4.DE.45 | Kyawthuite | Bi3+Sb5+O4 |
Fluorescence of Downeyite
None
Other Information
Notes:
Extremely hygroscopic. In air will deliquesce in a few minutes and be absorbed into substrate or evaporate leaving colorless film. Readily soluble in cold H2O, mineral acids, and acetone.
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 Downeyite
mindat.org URL:
https://www.mindat.org/min-1315.html
Please feel free to link to this page.
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External Links:
References for Downeyite
Reference List:
McCullough, James D. (1937) The Crystal Structure of Selenium Dioxide. Journal Of The American Chemical Society, 59 (5) 789-794 doi:10.1021/ja01284a004
Finkelman, Robert B., Mrose, Mary E. (1977) Downeyite, the first verified natural occurrence of SeO2. American Mineralogist, 62 (3-4) 316-320
Localities for Downeyite
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.
Italy | |
| Russo et al. (2004) |
USA | |
| Lapham et al. (1980) |
| Finkelman et al. (1977) |
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Burnside, Northumberland County, Pennsylvania, USA