VEINS. 



411 



ing will not as a rule be confined to a simple zone parallel witli the fissure, 

 bnt will reduoe only occasional masses of rock along the fissure to frag- 

 ments. Wiien in such cases ore and gangue minerals are subsequently 

 precipitated, the deposit will be confined to the main fissure where the 

 adj(Mning country is unbroken, but it will spread into the neighboring rock 

 whore crushing has occurred, the excrescent ore bodies being nev(irt]ieles> 

 merely lateral extensions of the filling of the fissures. .Afiners then usually 

 call the entire occurrence a fissure vein, and witli no little reason, since the 

 whole deposit is so evidently and closely dependent upon the existence of 

 a fissure. In some of the simpler cases of this kind even formalists will 

 grant the applicability of such a term as irregular vein or vein with irreg- 

 ular walls. "Pipe vein" has also sometimes been used to ex])ress structin'o 

 of this kind, but this term has been employed in such various senses as to 

 be objectionable. When the irregularity of the deposits is great, it has 

 been usual for mining engineers and geologists to describe rather than to 

 name them, to speak of stockworks and impregnations connected with 

 veins, and the like. It does not seem expedient, however, to designate ore 

 bodies so very closely related by difi^erent names unless the connection is 

 also expressed by some appropriate term. The connection existing between 

 the various portions of a deposit is at least as important as the form of the 

 various parts, and, if miners err in giving a wrong impression as to form, 

 the usual nomenclature of mining geologists ignores the close interdepend- 

 ence recoo-nized in the language of the miners. 



Fig. 20. Simple fissure rein and chambered vein. 



The form of deposit under discussion is illustrated in the above dia- 

 gram (Fig. 20 h). 



