Cerium group minerals

Most important mineral Lanthanum belongs to the light REM-group. the cerium group. Minerals typical forthis group are monazite (Ce,La,Nd,Th)(PO. SiO ). Figure M25 and bastnaesite. 

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. 

Bastnaesite belongs to the carbonatite group of minerals that contain REOEs. Beside the cerium group of elements, bastnaesite also contains yttrium and europium. Typically, it contains 65-75% REOE. Bastnaesite is usually found in pegmatites, carbonatite and hydrothermal ore bodies in alkaline gangue minerals. Because it is poor chemically and stable, it is not found in mineral sand deposits. 

Flotation Properties of Cerium Group of Reoe Minerals... 

FLOTATION PROPERTIES OF CERIUM GROUP OF REOE MINERALS... 

Neodymium occurs in nature in the minerals hastnasite, monazite, cerite and allanite. The element always is associated with other rare earths, especially cerium group elements. Its abundance in the earth s crust is about 0.0024%. 

The lanthanide contraction is probably the reason why the natural processes lead to fractionation and give rise to cerium group elements containing mainly the larger rare earth elements of lower atomic numbers, and to yttrium earth minerals containing mainly smaller rare earth elements with higher atomic numbers. Yttrium, although not a rare earth element, its atomic number 39 is low and its radius is similar to that of Ho. Thus yttrium appears with heavy rare earth elements. 

In the formulae for minerals Y Is to be msli.nttooil m representing yttrium group elements, and Ce, cerium group elements. 

None of these uses, however, seems destined to create any considerable demand for tho cerium group romisniudN, There is no concern about the supply of cerinm since all that is used nt the present time may lie considered as a by-product. If the demand should exceed this snppl.v, much cerium could lx extracted from minerals like allanife which are now not used. 

Monazite, the orthophosphate of the cerium group rare earths, is, without doubt, the most important rare earth mineral. It contains cerium-group oxides (49 to 74 per cent), yttrium-group oxides (1 to 4 per cent), thoria (1 to 20 per cent), and variable quantities of silica, iron (III) oxide, alumina, etc. Typical commercial samples of... 

Mineral Formula Cerium group earths, % Yttrium group earths, % Other oxides, %... 

At Baiyunebo in Inner Mongoha, 135 km from Baotou, RE minerals are found together with minerals of iron, titanium and niobium. The deposit is worked for iron, which keeps the costs low for production of the RE metals. Both monazite and bastnaesite are mined and, because of that, the mine is very important as a source of the cerium group metals. The bastnaesite has a higher content of samarium and europium than the CaHfornian ore in Mountain Pass. As the monazite is low in thorium and free from uranium its radioactivity is low, which is a benefit for ore handhng. 

Table 24.1 lists the major REO minerals of economic value. REO minerals are also divided into two sub-groups, complex and selective complex minerals, all containing lantanoids (from cerium to lutecium). The selective group contains elements from onto or the other group. 

---