ORE DEPOSITS 21 



for the purpose of shipping supplies to the mines and marketing 

 the ore or bullion; the question of dumping ground for the re- 

 moval of waste; the position of the mill for the reduction of the 

 ore, and position of the smelter for roasting the ore. 



(4) The geological and physical problems in connection with 

 < let i TII lining the mine deal perhaps more with the future of 

 the mine than with the actual cash value. In this connection 

 one must consider not only the enclosing rocks, their resistance, 

 definition and influence upon the mineralization, but must 

 consider also the fissure deposits, if they are present, the faults, 

 because in the majority of deposits the ore actually occurs in 

 fissures and faults, or as fissure veins. 



(5) Fissures and faults are additionally important because in 

 many cases the continuity of the ore body must be determined. 

 If faulted by intersecting fissures, this must be known and the con- 

 sequence actually determined. It is a well-known fact that ore 

 bodies are more often irregular in dip, strike, and formation than 

 otherwise, the valuable portion of ore being controlled by some 

 physical fact such as the intersection of the fissure with certain 

 strata whose definition is known, intersection of fissure with the 

 igneous rocks, and intersection of one fissure with another of dif- 

 ferent age. In a known district it is often possible by careful 

 observation of these facts to calculate the exact position of valu- 

 able bodies. At Rico, Colorado, vertical veins intersect a zone 

 of disturbance rich at the point of intersection. This has been 

 proven generally true. Therefore, wherever vertical veins in- 

 tersect a plane of disturbance, rich ore deposits are more likely 

 to be encountered. 



(6) Ore above or below water level is important on account of 

 the method of treatment of the ore. Above water level there are 

 frequently high-grade ores that can be quickly and cheaply 

 reduced by a simple mill upon the ground, whereas below water 

 level the milling process may be involved and expensive as it may 

 be necessary to smelt the ores before reduction to the metallic state. 

 These are very important items in the cost of reduction because 

 of the additional expense required and the uncertain factor or 

 the cost of reduction. 



(7) It is also necessary to say whether the ores are primary 

 or secondary in origin. Often there is a zone in the vein wherein 

 are deposited, below water level, very rich bodies of ore which 

 under normal conditions might reasonably be considered perma- 



