BY-PSODUCTS OF MINEBAL-LAND CLASSIFICATION. 155 



The Geological Survey does not make assays, not being provided 

 with the proper equipment or a sufficient force. Its assay work is 

 therefore done by custom assayers of established reputation. 



History of tTie region. — ^The question sometimes arises whether the 

 mining possibilities of a region are fairly represented by the extent 

 to which it is developed. If a region contains few prospects and no 

 mines, or if many of its prospects have been abandoned, is it or is it 

 not because valuable metalliferous deposits are really absent? Some 

 light may be shed upon this problem by the history of the region. 



If the region has long been accessible and is known to have been 

 well prospected, lack of development should have some weight against 

 classification of land as mineral. It must be considered, on the other 

 hand, whether local prejudice against some kind of country rock or 

 gangue material may not have lessened the value of prospecting, or 

 whether the region may not contain deposits of a kind that has not 

 been looked for. 



Abandonment of prospects may not always indicate the worthless- 

 ness of the lodes ; it is sometimes due to the miner's failure to recognize 

 valuable ores. Many metal prospectors have little knowledge of the 

 appearance of ores other than those of gold, silver, copper, and lead 

 and do not always recognize the secondary ores of copper, lead, and 

 zinc. For this reason the dumps of abandoned mines may reveal 

 ores of rarer metals or others not formerly used or commonly searched 

 for by prospectors. 



Mining methods and facilities often, of course, determine the suc- 

 cess or failure of a mine, and it is proper to consider in every case 

 whether abandonment may not have been caused by inefficient mining, 

 crudity of methods, or difficulty of transportation. The transpor- 

 tation problem may be largely disregarded, for if a region develops 

 good metalliferous deposits transportation is pretty certain to be 

 provided in time, but the presence or absence of roads and trails has 

 an important bearing on the accessibility of the region, which in 

 turn is a factor of prime importance in deciding whether the absence 

 of prospecting indicates the absence of valuable deposits. 



BY-PRODUCTS OF MINERAL-LANB CLASSIFICATION. 



VALTnE OF COLLATERAL INFORMATION OBTAINED. 



The process of classifying the public lands as to their mineral char- 

 acter involves the gathering of a large amount of information which 

 is not only essential to the classification but valuable for other rea- 

 sons. Furthermore, the accuracy and completeness of field observa- 

 tion necessary for classification afford an opportunity to record many 

 facts which are entirely extraneous to the classification itself but 



