Cerianite-(Ce)
{{Short description|Oxide mineral}}
{{Infobox mineral
| name = Cerianite-(Ce)
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| image = Cerianite-(Ce).jpg
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| caption = Yellow powder of the very rare mineral cerianite-(Ce) from Morro do Ferro, Caldas, Minas Gerais, Brazil.
| category = Oxide
| formula = {{chem|(Ce,|Th)|O|2}}
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| system = Isometric
| class = Hexoctahedral (m{{overline|3}}m)
H-M symbol: (4/m {{overline|3}} 2/m)
| symmetry = Fm{{overline|3}}m
| unit cell = a = 5.42 Å; Z = 4
| color = Dark greenish amber-yellow, yellow, buff
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| habit = octahedra; earthy, massive
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| diaphaneity = Translucent or transparent
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| density = 7.20 (synth. material, calc.; approximated)
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| other = 25px Radioactive
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| references = [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cerianite-%28Ce%29 Mineralienatlas]
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Cerianite-(Ce) is a relatively rare oxide mineral, belonging to uraninite group with the formula {{chem|(Ce,|Th)|O|2}}.{{cite web|url=http://www.mindat.org/min-929.html |title=Cerianite-(Ce): Cerianite-(Ce) mineral information and data |website=Mindat.org |accessdate=2016-03-04}}Graham, A.R., 1955. Cerianite CeO2: a new rare-earth oxide mineral. American Mineralogist 40, 560-564 It is one of a few currently known minerals containing essential tetravalent cerium, the other examples being stetindite and dyrnaesite-(La).{{cite web|url=http://www.mindat.org/min-38899.html |title=Stetindite: Stetindite mineral information and data |website=Mindat.org |accessdate=2016-03-04}}{{cite web|url=http://www.mindat.org/min-46510.html |title=Dyrnaesite-(La): Dyrnaesite-(La) mineral information and data |website=Mindat.org |accessdate=2016-03-04}}
Occurrence and association
Cerianite-(Ce) is associated with alkaline rocks, mostly nepheline syenites.{{cite web|url=http://www.handbookofmineralogy.org/pdfs/cerianite-(Ce).pdf |title=Cerianite-(Ce) - Handbook of Mineralogy |website=Handbookofmineralogy.org |accessdate=2016-03-04}} It may be found in carbonatites. Cerianite-(Ce) associates with minerals of the apatite group, bastnäsite-group minerals, calcite, feldspar, "fluocerite", "hydromica", ilmenite, nepheline, magnetite, "törnebohmite" and tremolite. It is the most simple cerium mineral known.
Notes on chemistry
Crystal structure
For details on crystal structure see cerium(IV) oxide. Both ceria and thoria have a fluorite structure.