A new canvas in the hall of minerals — the "Shovel-Pit" of Ely. Xcvada. This was 

 painted by Albert Operti and presented to the American Museum by the Xevada Consoli- 

 datetl Copper Company through its president, Mr. S W. Eccles 



the wide dissemination of the copper ore, were led into a calculation of the 

 ultimate magnitude of the resources of the area. Prof. Andrew (". Lawson 

 of the I'niversit}' of California made a geological survey of the district, and 

 under the guidance of his conclusions, these capitalists secured the more 

 promising grounds. The company became well financed antl aggressive 

 mining was pushed with astonishing results. 



As to the geology of the Robin.son Canon, the region is a limestone forma- 

 tion into which, at a long distant time in the past, bodies of molten rock have 

 penetrated bringing with them copper minerals which have remained both 

 in the intruding rock and in the limestone, especially on the south side of 

 the canon. These copper minerals are for the most part sulphides, although 

 the action of the water carrying oxygen has through many sections of the 

 hills converted the sulphides into carbonates (green malachite), and the 

 lower layers of the formation have also from the beginning been slowly 

 enriched by having transferred to them the copper contents of the over- 

 lying beds. Sulphides with a low percentage of copper have in this process 

 been changed or mi.xed with sulphides of a higher percentage and this 

 secondary zone of enrichment as it is called, contains the most valuable 

 ore. Below this again are the prinuiry beds which have not been en- 

 riched in this way and whose mining l)ecomes a ({uestion for ■metallurgical 

 economics. 



The work is carried on through the agency of j)owerful steam shovels 



110 



