1908 ] 
Monazite and Monazite Mining 
83 
determined that in machines of this type the magnetite can be 
removed when the amperage is .2; ilmenite with 1.1; chromite 
with 1.6; garnet with 1 .75; hypersthene and olivine with 2.2; mon- 
azite with 3.5 amperes. Zircon is left behind with the gold as 
non- magnetic. Any platinum that might be present would begin 
to be lifted by the weakest current, but most of it would not be 
lifted until the current was 1.5 amperes. 
It is possible to separate almost completely pyrite from horn - 
blende by picking out the hornblende with the electro-magnet, the 
pyrite remaining in the tailings. Such minerals as pyroxene, epi- 
dote, titanite, tourmaline, and serpentine are readily picked out 
by the Wetherill magnetic separator with a current of 2 to 2.5 
amperes. Brookite and cassiterite can occasionally be picked out 
with an amperage of 3.5. 
USES OF MONAZITE 
The commercial value of monazite depends upon the incandes- 
cent properties of the rare earth oxides which it contains, such as 
cerium, lanthanum, didymium and thorium oxides, which are 
used in the manufacture of the Welsbach and other incandescent 
gas light mantles. It is the thoria that is used in largest amount 
and which gives the actual value to the monazite. In the reduc- 
tion of the monazite sand, there are a number of the rare earth 
salts that are obtained in considerable quantity, which has made it 
possible to carry on an extensive series of experiments with these rare 
earth oxides. It requires from 4 to 6 months to recover from the 
monazite sand its percentage of thoria and render it sufficiently 
pure to be used in the mantles. 
The Welsbach light consists of a cylindrical hood or mantle com- 
posed of a fibrous network of the rare earths, the top of which is 
drawn together and held by a loop of asbestos or platinum wire. 
When in use, this mantle is suspended over the flame of a burner, 
constructed on the principle of the Bunsen burner, in which the 
heating instead of the illuminating power of the hydrocarbon of 
the gas is used by burning it with an excess of air. In this man- 
ner the mantle becomes incandescent and glows with a brilliant 
and uniform light. 
