64 
IOWA ACADEMY OF SCIENCES. 
RECENT DEVELOPMENTS IN THE DUBUQUE LEAD 
AND ZINC MINES. 
BY A. G. LEONARD. 
During the past year or two there have been some important 
developments In the Dubuque district. New lead mines have 
been opened up, new ore bodies have been discovered* and the 
Durango zinc mine, the largest in the state, has been still 
further developed. 
About one mile west of the city is located the mine of the 
Dubuque Lead Mining company, which has been worked only 
about a year and a half. It is on the west end of the old level 
range which has been followed for nearly three miles and has 
yielded considerable ore from various points along its length. 
When the mine was visited in November, 1895, there were 
seventy -five men employed and the place presented a lively 
appearance. The three shafts are 210 feet deep with a steam 
hoist -on one and gins on the other two. The company has 
just erected a concentrator at the mine for the purpose of 
crushing and cleaning the ore. This was made necessary by 
the fact that in this mine much of the Galena occurs scattered 
through the rock, sometimes in particles of considerable size. 
The limestone is crushed and the lead then separated from it 
by washing. The ore-bearing dolomite forms a zone from two 
to four feet wide and contains an abundance of iron pyrites. 
This latter mineral is often found here crystallized in beautiful 
octahedrons with a length of from one-fourth to three-fourths 
of an inch. Besides being disseminated through the rock the 
Galena occurs in large masses in what is probabij^ the fourth 
opening, and it likewise fills the crevice above for some dis- 
tance. The ore body is apparently an extensive one; 700,000 
pounds of lead have already been raised. Work in this mine 
is made possible only by the constant operation of a steam 
pump which keeps the water below the opening where the ore 
occurs and thus allows the miners to reach the deposits. 
