Iiiflnciicc of Country Rock. — Weed. 
and continuous in one rock, splits up, forming' horses or drop- 
pers, or, if very extensive, becomes a zone traversed by many 
small parallel threads and stringers, too small to be worked. 
This is discussed by Prof. Beck, in his recent book,* from 
which Fig. i is taken. 
In the Guadalupe mine, Chihuahua, Mex., a vein, carrying 
a solid ore from lo to 40 feet wide, changes eastward into 
many small branches, too small to be worked, though the rich- 
ness of the ore in them may be unchanged. 
Where veins traverse foliated rocks, such as gneisses and 
schists, the original fissures may have been due to a very slight 
movement along the line of schistosity, and the result may be 
linked veins, composed of numerous connected lenses, such as 
are commonly found in the Piedmont area of the Carolinas. If 
the movement is distributed over several folia the vein is not a 
simple one, but consists of a series of lenticular Jiiasses over- 
lapping each other, and these may occur in a zone ; so that the 
"vein" may be several hundred feet wide. 
1 clay selvage 
Roof of level Tig. 2 , / 1 no trace of ore* 
3.> 
Section of Level, showing the Florence Vein, Neihart, Mont., 
crossing an Amphibolyte Dike in Metamorphic Schists. 
It is evident that, since different rocks break in different 
ways, the character of the fissures formed in them will depend 
on the counti"y-rock. Excellent examples of the various effects 
due to the texttire, cleavage, hardness, and other properties of 
the rocks, are to be seen in the silver-lead mines at Neihart, 
Montana, where steeply-dipping metamorphic rocks are cut by 
a large and very irregular intrusion of dioryte, and both are cut 
by later intrusions of rliyolyte porphyry. Well-defined fissure- 
veins cross all these rocks. The metamorphic rocks consist of 
alternating bands of feldspathic gneiss with softer, more schist- 
ose micaceotis rocks, and, more rarely, tough amphiboly tes. 
The veins cross these rocks at nearl y right angles to the 
• Lehre von den Erzlagerstnttenlehre, Berlin. 1901, p. 135. 
