* Argentite: Ag2S for production of silver
    * Chromite: (Fe, Mg)Cr2O4 for production of chromium
    * Gold: Au, typically associated with quartz or as placer deposits
    * Uraninite (pitchblende): UO2 for production of metallic uranium
I can't seem to find anymore. :'( 
Could somebody help get the ball rolling.
platinum
Iridium
Titanium