202 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213; 
The deposit as a whole has roughly the form of either a truncated 
cone or a dome, both types being commonly associated with an irreg- 
ularly circular or elliptical area of shale at the surface, over this 
central portion. The ores of the circles arc 4 similar in character to 
those described under linear deposits. In all the important cases 
studied, the circle has been formed by the intersection of faults. 
Small circular deposits are sometimes developed on the flanks of a 
dome produced by folding. In all the circular deposits near the city 
of Joplin which were examined, the inner walls were of the dolomitized 
limestone with chert. 
The vertical extent of the ore body, in both linear and circular 
deposits, may be limited to a few feet or it may continue for a hundred 
feet or more. The occurrence of the ore is not confined to a particular 
horizon, but it may be met at any level where the conditions were 
favorable for Ms deposition, and it maybe found at several levels, 
one above another, with barren or nearly barren ground between. 
Under the head of irregular deposits may be included all such ore 
bodies as do not correspond to any of the foregoing types. They are 
formed in breccias due either to complex folding or faulting, or to 
folding combined with faulting, and have no definite form. They 
may in most cases be considered as combinations of types already 
described. 
Individual runs of ore, associated with one or more faults or folds, 
may have a horizontal extent ranging from a few feet to one-fourth 
mile or more. Although there are areas in which no systematic 
arrangement of the individual ore bodies can be discerned, in most 
cases they can be grouped along a zone of faulting or folding, within 
which they mayor ma\ not show a general Linear or parallel arrange- 
ment; or the main lines parallel to the general direction of the zone 
m;i\ be associated with minor lines a1 an angle with it. Such zones 
usually have the same general trend as the main system of faulting 
for the part of the district in which they occur. There are several 
important systems of faults and folds in the Joplin district which 
vary somewhat in direction from place to place, and of which the 
most prominent throughout the district has a general northerly or 
northwesterly trend. A second important system having a general 
easterly or northeasterly direction sometimes predominates, though it 
is usually associated with the other and subordinate to it. 
The principal structural disturbances of the Joplin district appear 
to have been concentrated along certain lines or belts having the 
same general trend as the more pronounced zones of ore deposits, 
which group themselves roughly along these belts. The three main 
belts of the district are (1) the Jojuin belt, including the zones imme- 
diately around Joplin and northward to Tuckahoe, with the outlying 
groups southward to Shoal Creek and northwesterly to Carl Junction; 
(2) the Galena belt, including the deposits around Galena and just 
