206 TRANSACTIONS OF THE 
be successfully accomplished. It may be that the gangue 
minerals are of such a nature as to interfere materially 
with the treatment proposed as indicated by the charac- 
ter of the ore, or that the respective minerals exist in 
a condition of such intimate association that ordinary 
methods of treatment would prove unavailing. 
The most logical way in which many of the physical 
characteristics of an ore and its components may be 
determined is by microscopic examination and it is im- 
portant that these features should be known before ex- 
perimental work has actually been commenced. A knowl- 
edge of the physical characteristics of an ore and the 
minerals composing it, gained by microscopic study, to- 
gether with the information supplied by chemical analysis 
should form a basis for the experimental testing work 
which is to be conducted. Cut and try methods of ore 
testing are expensive since they not only consume con- 
siderable time but also require making hundreds of 
chemical analyses which are expensive and in the end 
the deductions based on these methods of procedure may 
be open to grave and well founded doubt. The diffi- 
culties encountered in testing may be caused by unknown 
physical characteristics of the minerals in the ore or 
their mode of association or may be of a mechanical 
nature. In many instances it is only after considerable 
sums of money have been spent in cut and try experimen- 
tal work leaving results still in doubt that the microscope 
is applied as a means of last resort. While the micro- 
scope will not prove a means of solving all the problems 
which may arise in the treatment of ores yet it can be 
relied upon to furnish information that cannot fail to 
prove of value and when this information is available 
for application during the preliminary testing the value 
of its use is proven by the elimination of unnecessary 
time and labor involved in costly chemical analyses. If 
the physical characteristics of the minerals in an ore to- 
gether with their mode of association are known the 
selection of a proper method of treatment and the crea- 
tion of conditions most favorable for obtaining good 
results are a matter of much less experimentation. 
It is only after all the obtainable information con- 
