The two most important ores from which rare earths are extracted are monazite and bastnasite. Monazite is a rare earth-thorium orthophosphate usually found in sand beach platters in deposits located in India, Ceylon, Brazil, Australia, USA and South Africa. Bastnasite is a rare earth fluorcarbonate and the largest deposits are located in California. Both monazite and bastnasite contain residual amounts of thorium oxide (ThO2) which is responsible for the radioactivity of these ores.