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It's a showdown with rare earth elemental ore Monazite-(Ce) and index mineral Andalusite.
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Biotite from
LaSalle County, Illinois, USA


Locality type:County
Classification
Species:'Biotite' (not an IMA approved species)
Formula:K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2
Confirmation
Validity:Believed Valid
Data
Mineral Data:Click here to view Biotite data
Locality Data:Click here to view LaSalle County, Illinois, USA
Data Identifiers
Mindat Occurrence Record ID:859333
Long-form Identifier:1:3:859333:7
GUID (UUID V4):0
References
Lidak,E.G.,Marvin,R.F.,Thomas,H.H.,and Bass,M.N.,(1966) Geochronology of the Midcontinent Region ,United States,Part IV, Eastern Area:Journal of Geophysical Research,v.71,p.5427-5438
 
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