From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland,  55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-6
PRASEODYMIUM (Gr. prasios, green, and didymos, twin), Pr; at. wt. 140.9077; at. no. 59; m.p. 931 C; b.p. 3512 C; sp.gr. (alpha) 6.773 (beta) 6.63;  valence 3 or 4.  In 1841 Mosander extracted the rare earth didymia from earth, samaria, from didymia obtained from the mineral samarskite.  Six years later, in 1885, von Welsbach separated didymia into two other earths, praseodymia and neodymia, which gave salts of different colors.  As with other rare earths, compounds of these elements in solution have distinctive sharp  spectral absorption bands or lines, some of which are only a few Angstroms wide.  The element occurs along with other rare-earth elements in a variety of minerals.  Monazite and bastnasite are the two principal commercial  sources of the rare-earth metals.  Ion-exchage and solvent extraction techniques have led to much easier isolation of the rare earths and the cost has dropped greatly in the past few years.  Praseodymium can be prepared by several methods, such as by calium reduction of the anyhydrous chloride or fluoride.  Misch metal, used in making cigarette lighters, contains about 5% praseodymium metal.  Praseodymium is soft, silvery, malleable, and ductile.  It was prepared in relatively pure form in 1931.  It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium or neodymium, but it does develop a green oxide coating that spalls off, when exposed to air.  As with other rare0earth metals i should be kept under light miiineral oil, or sealed in plastic.  The rare-earth oxides, including Pr2O3 are amoung the most refractory substances known.  Along with other rare earths, it is widely  used as a core materal for carbon arcs used by the motion picture industry for studio lighting and projection.  Salts of praseodymium are used to color glasses and enamels; when mixed with certain other materials, praseodymium produces an intense and unusually clean yellow color in glass.  Didymium  glass, of which praseodymium is a component, is a colorant for welder's goggles.  The metal (99+ % pure) is priced at about $2.00/gm.