UTAH ACADEMY OF SCIENCES 153 
ficulty of treatment is the low grade oxidized ore. It is 
too low in value to ship and treat at a smelter and does 
not lend itself well to gravity methods of concentration 
so far developed. There is an abundance of this kind of 
ore awaiting some suitable method for the extraction of 
its values. Included with the unmined low grade ore 
bodies are also tailing dumps from previous metallurgi- 
cal treatment. Two methods of handling such ore 
which are receiving much attention give promise; these 
are choridizing roasting and volatilization, though of 
course there are other possibilities. 
Chloridizing roasting is a pyrometallurgical oper- 
ation followed by some such hydrometallurgical process 
as brine leaching. While chloridizing roasting itself is 
not new, its application to extraction of lead, copper, 
and silver from oxidized ores in connection with brine 
leaching has recently come in for much experimentation. 
The process consists in blast roasting a mixture of ore, 
salt, pyrite, or other sulphur bearing material, and in 
some cases fuel such as coal. The reactions involved are 
those taking place between the salt, sulphur products, 
gangue, water vapor, and metal-bearing mineral, all or 
in part, to produce a chloride of the metal. This renders 
the metals soluble in brine and the process from this 
stage is a hydrometallurgical one. The Tintic Milling 
Company is operating such a process on a copper-silver ore 
at Silver City in the Tintic District in Utah. 
The volatilization process is a chloridizing process 
differing from that just mentioned in that the chlorides 
are leached with the furnace gases rather than with the 
brine solution. A further difference is that sulphur is 
not essential to the chloridizing reaction, and in amounts 
much above 5 per cent, is a detriment. The following 
steps are involved: furnacing a mixture of ore with some 
chloridizer such as salt or calcium chloride at sufficient 
temperature to effect volatilization of the chlorides of 
the metals as formed; collection of the volatilized chlo- 
ride and reduction of the fume with lime and carbon to 
form bullion and calcium chloride slag. The calcium 
chloride slag may be returned to the first step in the 
operation. The furnacing may be carried on in a cement 
kiln and the fume may be caught by a standard Cottrell 
