278 
VADOSE ORE DEPOSITION 
demonstrated in arid lands, there is really among ore deposits an 
important facies which is not always conspicuously displayed un¬ 
der conditions of moist climate. At the bottom of the distinctly 
oxidized ores and between them and the so-called primary sulphide 
ores in fissure-veins, is a bonanza sulphide-zone, the materials of 
which are as truly products of vadose origin as are the rusty 
ores above. This is a distinction that Posepny did not make; and 
the lack of it led him into insuperable difficulties. 
Clear distinction between vadose ore-formation as a general 
geologic process and the superficial change of mineral veins to 
gossan as a local effect, appears to have been first pointed out in 
the instance of the lead and zinc deposits of the Ozark region. 
Coming at a time when Posepny’s paper was under warm public 
discussion Winslow’s presentation ® of this phase of the subject 
did not attract the attention which it really deserved. With some 
objections removed, as I have elsewhere explained,^ and by the* 
application of somewhat broader principles permitted by the in¬ 
vestigations of another decade,® a still wider generalization is not 
only possible but practically valuable. 
Transferring the suggestions to the arid regions full dataware 
at once obtained for the establishment of a great genetic class of 
ores, formed wholly and independently within the vadose zone. 
The validity of this group is well shown by the universality with 
which its various members are recognizable. Even in such a - 
moist climate as that in which the Ozarks are situated we may 
have the apparent anomaly of an “eisener Hut” covering a sul¬ 
phite ore deposit all the materials of which are derived directly 
and solely from vadose deposition. 
In point of origin only a part of vadose ores really constitute 
gossans. Although it is not usually so regarded, the genesis of 
the ores of the vadose zone and of those originating from the 
depths of the earth is mainly and fundamentally different. On 
the whole, it is surprising at how few points the ores of the zones 
actually touch. That these two classes of ores were so long con¬ 
fused, or rather that they were not earlier differentiated, seems to 
be due chiefly to the fact that detailed investigations of ore-genesis 
were principally carried on in lands of moist climate where the 
3 Missouri Geol. Surv., Vol, VII, p. 477, 1894. 
4 American Geologist, Vol. XXV, p. 355, 1901. 
5 Trans. American Inst. Mining Eng., Vol. XL,, p. 184, 1909. 
