Cerium is a lanthanoid and the most abundant of the rare earth elements. It is used in catalytic converters, as well as in optics for precision polishing. Cerium is found in the minerals monazite and bastnasite
Molycorp - http://www.molycorp.com/products/cerium.html - Molycorp is a mining and marketing subsidiary of Chevron (NYSE: CVX) that produces cerium, in addition to molybdenum and other rare earth elements.
Commerce Resources Corp. (CVE: CCE)
Great Western Minerals Group (CVE: GWG)
Metall Rare Earth Limited - http://www.metall.com.cn/ce.htm American Elements - http://www.americanelements.com/ce.html - Cerium metal, cerium oxide, cerium acetate, cerium carbonate, cerium hydrate, cerium nitrate, cerium ammonium nitrate, cerium chloride, cerium fluoride, cerium 55 concentrate, cerium bromide, cerium oxalate, and cerium sulfate.
Avalon Rare Metals (TSE: AVL)
Cerium News 2010-02-01 - (ta) - More rare earths, more gold, less gas