102 University Geological Survey of Kansas. 
Third, Deleterious Water.—A great deal of ground water 
and surface pond water in the mining district is exceedingly 
deleterious, due to the presence of a comparatively large 
amount of free sulphuric acid and soluble sulphates. This 
condition is brought about almost entirely by recent oxida- 
tion of sulphides, principally pyrite and marcasite, FeS,, but 
in part by oxidation of zine blende, ZnS. Mining operations 
produce large underground openings, the walls of which are 
always damp. In the walls a great deal of the sulphides 
mentioned are exposed to the air, and the better the mine is 
ventilated the greater will be the supply of oxygen to produce 
the oxidation. In this way iron is changed to a soluble iron 
sulphate, which, of itself, has a bad effect on iron castings 
and pipes. But still worse, the process of oxidation produces 
free sulphuric acid which acts so vigorously on iron with 
which it is brought in contact that it is exceedingly destructive. 
The change brought about by this oxidation may be repre- 
sented as follows: FeS,+7 O+H,O—=FeSO,+H,SO,. The 
free sulphuric acid is so abundant in different places that its 
corrosive action on iron piping is surprisingly great. In one 
instance on the Mastin land new gas pipe was used as a sup- 
ply pipe for a pump, and in nineteen days’ use holes were 
made in it so that it was worthless. The surface of the pipe 
was bright as though just taken from a strong acid solution. 
Old mines which have stood open for some time are worse 
than new mines, and mines in solid flint rock are worse than 
those having limestone exposed to the mine water. This is 
true to so great an extent that a careful examination was 
made, resulting in a failure to discover a single mine with 
bad water where limestone in any considerable quantity was 
found in the mine. It is currently reported throughout the 
entire Joplin area that mine water is worse at Galena than 
anywhere else. This is because flint rock is so abundant and 
limestone so scarce, and, further, zinc ore is more intimately 
mixed with pyrite here than elsewhere. 
Tests were made in many places to learn whether or not 
ground water generally had an acid reaction. It was found 
that in all cases where mines had been opened for years 
within solid flint areas the water was acid, usually very acid, 
