VADOSE ORE DEPOSITION 
383 
special features and peculiarities of geologic structures in their 
relations to ore-genesis are brought out into bold relief. 
Commonly, in normally moist climates when ore deposits have 
been most critically considered in regard to their origin, their va- 
dose relationships are passed over. In an arid climate the vadose 
ores often constitute the entire workable deposits. If they are 
at all connected with profound phenomena, the latter are quite 
unimportant. 
Although miners are not always disposed to admit it, it is 
a well-known fact that they rely much more than they would 
have us suppose upon geologic structures as clues to ore-bodies. 
Dependent upon geologic structures as often is the segregation 
of ore-materials into workable masses, the direct association of 
the two phenomena is shown at its best only in the greatly broad¬ 
ened vadose-zone of the arid regions. Under climatic conditions 
of this kind, and where the vadose zone is often more than a 
thousand feet in depth, so close is the relationship that distinctive 
types of deposits are establishable based upon geologic structure 
alone. With the ready determination of the structural type of 
an ore-body its general shape is at once surmised and the best 
method of its exploration indicated. This was the end really 
sought when the geometric form of ore-bodies was thought to be 
so important a determination in mining. 
These structures apply to stratified, igneous and metamorphic 
rocks alike. In the case of the stratified rock-masses somewhat 
nicer distinctions are of course possible among the geologic struc¬ 
tures producing impondment conditions than in instances of 
'either igneous or metamorphic rocks. 
Mining men are prone to attach great practical importance to 
the shape of ore-deposits, but scientists, especially of late, seem 
inclined to belittle this feature somewhat, and to emphasize the 
more obscure genetic features. In the classification of ore- 
deposits it may be even questioned whether even the cruder dis¬ 
tinction according to shape has not, scientifically as well as prac¬ 
tically, many advantages over the strictly genetic method. Such 
plans as those proposed long ago by Waldauf von Waldtenstein 
Cotta ® Eottner and Serlo and later by Kohler ® and by 
5 Die besonderen Dagerstatten der nutzbaren Mineralien, I, Band, 1824. 
6 Dehre von den Erzlagerstatten, I. Band, 1859. 
7 Deitfaden zur Bergbaukunde, 1869. 
8 Lehrbuch von Bergbaukunde, 1884. 
