1 1 6 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



As there is an unquestionable connection in depth between the various 

 ore-bearing regions of the Ruby Hill deposits, if this nomenclature is cor- 

 rect the ore bodies are to be regarded as branches of a single lode. Never- 

 theless, the fact is that these deposits differ essentially from those which 

 yielded the usually accepted definition of the words vein and lode, and the 

 analogies between the two varieties are so distant that an attempt to apply the 

 terminology of typical veins to the Ruby Hill deposits as a whole leads 

 immediately to misunderstandings. In ordinary veins ore is deposited in 

 pre-existing openings, while the bodies of Ruby Hill were mainly deposited 

 by substitution. In ordinary veins nearly all the space not occupied by 

 fragments of rock is filled with ore and other minerals. In the Eureka 

 occurrence many of the fissures have served merely as channels for the 

 solutions, and space for deposition has been provided mainly by chemical 

 means. The bearing of those differences is readily made apparent. In 

 typical lodes a fragment of country rock entirely inclosed within the fissure, 

 and hence completely and substantially surrounded by ore and gangue 

 minerals, is called a "horse," but a mass of rock divided from the surround- 

 ing country by mere cracks not filled with vein matter is not called a horse. 



The term "horse" is usually unequivocal and signifies a mass of country 

 rock of considerable size entirely inclosed in ore or vein matter. One can 

 always conceive, however, of the croppings of a vein being eroded to the level 

 of the center of a horse, one surface of which would then be exposed to the 

 air, and the horse would not be entirely inclosed by ore and gangue. 

 Masses of rock in the croppings of a lode when they resemble horses in 

 other respects are therefore known by the same name. No definite limits 

 can be assigned to the size of a true horse, which certainly depends upon 

 the size of the lode as well as upon individual opinion. Nevertheless, 

 although there are horses in the Gomstock lode a few hundred feet wide, it 

 would be a most extraordinary lode that would contain a horse exceeding 

 1,000 feet in width, and the limestone wedge of Ruby Hill is much wider 

 than that on the surface. All miners will probably agree that a horse must 

 be a portion of the contents of a vein or lode. 



In the mineral zone of Ruby Hill many masses of rock are surrounded 

 by fissures, most of which are mere fault seams, though some of them have 



