ORES OF LEAD. 147 
ably for their extent. ‘They occur in limestone, in the States 
of Missouri, Illinois, Iowa, and Wisconsin ; argillaceou’ 
iron ore, pyrite, calamine and smithsonite (‘‘dry bone” of 
the miners), blende (‘‘black-jack”), carbonate of lead or 
cerussite, and barite or heavy spar, are the most common 
associated minerals; and less abundantly occur chalcopy- 
rite and malachite, ores of copper; also occasionally the 
lead ores, anglesite and pyromorphite ; and in the Mine La 
Motte region, black cobalt, and linneite an ore of nickel. 
Lead ore was first noticed in Missouri in 1700 and 1701. 
In 1720 the mines-were rediscovered by Francis Renault and 
M. La Motte; and the La Motte bears still the name of the 
‘latter. Afterward the country passed into the hands of 
Spaniards, and during that period, in 1763, a valuable mine 
was opened by Francis Burton, since called Mine a Burton. 
The lead region of Wisconsin, according to Dr. D. D. 
Owen, comprises 62 townships in Wisconsin, 8 in Iowa, and 
10 in Illinois, being 87 miles from east to west, and 54 miles 
from north to south. ‘The ore, as in Missouri, is abundant, 
and throughout the region there is scarcely a square mile 
in which traces of lead may not be found. The principal 
indications in the eyes of miners, as stated by Mr. Owen, 
are the following: fragments of calcite in the soil, unless 
very abundant, which then indicate that the vein is wholly 
calcareous or nearly so ; the red color of the soil on the sur- 
face, arising from the ferruginous clay in which the lead is 
often imbedded ; fragments of lead (‘‘ gravel mineral”), 
along with the crumbling magnesian limestone, and den- 
dritic specks distributed over the rock; also, a depression of 
the country, or an elevation, in a straight line; or “ sink- 
holes ;” or a peculiarity of vegetation in a linear direction. 
The ore, according to Whitney, occupies chambers or open- 
ings in the limestone instead of true veins, and in this 
respect it is like that of Derbyshire and Northern England. 
The mines of Wisconsin and Tlinois are in Lower Silurian 
limestone of the Trenton period, called the Galena lime- 
stone; those of Southeastern Missouri, situated chiefly in 
Franklin, Jefferson, Washington, St. Francois, St. Géne- 
vieve, and Madison counties, are in the ‘* Third Magnesian 
limestone ;” also Lower Silurian, but, of the Calciferous or 
Potsdam period ; those of Southwestern Missouri, situated 
mostly in Newtown, Jasper, Lawrence, Green and Dade- 
counties, and in the western part of McDonald, Barry, 
