Monazite scandium

The heavy mineral sand concentrates are scmbbed to remove any surface coatings, dried, and separated into magnetic and nonmagnetic fractions (see Separation, magnetic). Each of these fractions is further spHt into conducting and nonconducting fractions in an electrostatic separator to yield individual concentrates of ilmenite, leucoxene, monazite, mtile, xenotime, and zircon. Commercially pure zircon sand typically contains 64% zirconium oxide, 34% siUcon oxide, 1.2% hafnium oxide, and 0.8% other oxides including aluminum, iron, titanium, yttrium, lanthanides, uranium, thorium, phosphoms, scandium, and calcium. 

Scandium is very widely but thinly distributed and its only rich mineral is the rare thortveitite, Sc2Si20v (p. 348), found in Norway, but since scandium has only small-scale commercial use, and can be obtained as a byproduct in the extraction of other materials, this is not a critical problem. Yttrium and lanthanum are invariably associated with lanthanide elements, the former (Y) with the heavier or Yttrium group lanthanides in minerals such as xenotime, M "P04 and gadolinite, M M SijOio (M = Fe, Be), and the latter (La) with the lighter or cerium group lanthanides in minerals such as monazite, M P04 and bastnaesite, M C03F. This association of similar metals is a reflection of their ionic radii. While La is similar in size to the early lanthanides which immediately follow it in the periodic table, Y , because of the steady fall in ionic radius along the lanthanide series (p. 1234), is more akin to the later lanthanides. 

Scandium is found in ores of wolframite in Norway and thortveitite in Madagascar. It is also found in granite pegmatites and monazites. It is common in many of the ores where tin and tungsten are also found. 

Scandium, yttrium, and lanthanum, in group Ilia of the periodic table, usually occur in nature with the fourteen rare-earth elements, cerium (atomic number 58) to lutetium (atomic number 71). All of these elements except promethium (which is n ade artificially) occur in nature in very small quantities, the principal source being the mineial monazite, a mixture of rare-earth phosphates containing also some thoriurn phosphate. 

Scandium is thought to occur in more than 800 different minerals. Its most important ores are the minerals thortveitite and wolframite. It is also found in minerals containing other rare earth elements, such as monazite, bastnasite, and gadolinite. 

Bernhard F, Walter F, Ettinger K, Taucher J, Mereiter K (1998) Pretulite, SCPO4, a new scandium mineral from the Styrian and lower Austrian lazulite occurrences, Austria. Am Mineral 83 625-630 Boatner LA, Sales BC (1988) Monazite. In Radioactive Waste Forms for the Future. Lutze W, Ewing RC (eds) Elsevier North-Holland, Amsterdam, Ch 8... 

Occurrence Yttrium is a rare earth element and occurs in nearly all of the rare earth minerals. Rare earths are defined as a group of 17 elements, comprised of scandium, yttrium, and the lanthanides. The similar radii and oxidation states of the rare earths allows liberal substitution of the rare earths for one another into the crystal lattice sites of minerals. This substimtion accounts for their wide dispersion in the earth s crust and the characteristic occurrence as a group of elements within more than 100 minerals. The principal ores of the rare earths are basmasite, monazite, and xenotime. Several of the ores occur in unique geologic settings, whereas others are found in similar occurrences worldwide. 

For yttrium, on the other hand - fourth among rare earths and almost as rare as scandium - large resources are available as monazite, xenotime and ion-adsorption ore. A quantity of 2400 tonnes of yttrium oxide was produced in 2000, of which 2300 tonnes was mined in China. Of course, this concentrated production influences the price. In 5-kg quantities the price for 99.9% yttrium metal with less than 0.15% oxygen is US 100-150 per kilogram. 

Stubican and Roy (1963a) observed on quenched samples that the orthovanadates and orthoarsenates of scandium and of the lanthanides from Pr to Lu undergo a transformation from the tetragonal xenotime (= zircon) or the monoclinic monazite... 

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