In geology, the mineral bastnasite is one of a family of three carbonate-fluoride minerals. There is bastnasite-(Ce) with a formula of (Ce, La)CO3F. There is bastnasite-(La) with a formula of (La, Ce)CO3F. There is also bastnasite-(Y) with a formula of (Y, Ce)CO3F. Most bastnasite is bastnasite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnasite and the phosphate mineral monazite are the two largest sources of cerium. The hardness of bastnasite ranges from 4 to 4.5. The specific gravity ranges from 4.7 to 5.0, which is above average for a mineral.
In the case of bastnaesite, as described in Deco Trefoil, p.9, (November-December, 1967), a precalcination of the mineral may be employed, which makes it possible to solubilize only a part of the cerium with the mixture of the other rare earths during the subsequent recovery operation using hydrochloric acid.
The leaching of bastnaesite with a solution of nitric acid enables the selective solubilization of the trivalent rare earths to the exclusion of the cerium values, the soluble traces of which are principally in tetravalent form.
The first stage of the process of the invention entails calcining the bastnaesite at a temperature sufficiently high to transform the trivalent rare earths into a form capable of being solubilized in the subsequent nitric acid leaching step and converting the cerium into a form less soluble than the transformed trivalent rare earths.
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