324 QUICKSILVER DEPOSITS OE THE TACIFIC SLOPE. 



not a solid mass, but that subordinate fissures and ore channels exist in it. 

 This would be still more evident were all the ore bodies represented. Those 

 which have been exploited since systematic work was begun are, I believe, 

 all accurately given, but in the early days there were many openings, 

 resembling burrows rather than mines, excavated from the surface between 

 the Randol shaft and the top of Mine Hill. Mr. Reade has shown many 

 of the dumps of these old workings on Atlas Sheet VIII. They produced 

 considerable quantities of ore. One of them, the Juan Vega, which appears 

 on the plan but not on the sections, I was able to explore. The stopes were 

 of considerable size and the ore ajjpears to have been ver}- rich. It was 

 associated with masses of dolomite similar to those found at the surface as 

 croppings, but which are not met with in the lower levels. Evidently fis- 

 sures carrying ore in solution must have reached the Juan Vega and other 

 similar deposits. These fissures must have connected with great ore clian- 

 nels, and must therefore intersect the wedge of country rock. 



The wedge of rock between the two principal fissures has contained 

 ore bodies and the fissures leading to them must penetrate the wedge through 

 and through. The entire mass should be regarded as potentially ore bear- 

 ing and should be explored. It is not in the least likely that all tlie ore 

 which it contains is known and, if other bodies are encountered, they will 

 be mined at a greater profit than similar bodies at lower levels. This niciss 

 and the lateral extensions of the main fissures constitute the promising 

 ground in the mine. At the lowest levels reached there is little ore. There 

 is no known reason why bodies of cinnabar should not be found at still 

 greater depths, but I do not regard it as probable that the ore chambers 

 beneath the 2,000-foot level will be as frequent as they were above Some 

 further comments on the fissure system of this mine will be made below. 



Cora Blanca and Washington deposits Thc WOrkiugS of the WasllingtOU sliaft, 



which were formerlv known as the San Francisco mine, are connected 

 with the main mine of New Almaden, but the deposits were not being 

 worked during n\v visit. The association of minerals and rocks is entirely 

 similar to that of the main mine, and the deposits are also accompanied by 

 clay seams or alta.s. The position of the deposits is shown on Atlas Sheets 

 VIII, IX, ;\n(l X. Oix' has l)een followed in the- workings to a dejith of 



