THE GUADALUPE. 327 



only under exceptional conditions that ore bodies can be foreseen in the 

 quicksilver mines, and predictions as to the quantity of ore in these mines, 

 excepting so for as the ore is in sight, are entirely valueless. 



Minor deposits. — In additiou to the mines upon which notes liave Ijeen given 

 above, there are a number of workings which have yielded cinnabar in 

 quantities of little or no commercial importance, but which throw some light 

 on the structure of the country through their position relatively to the more 

 developed deposits. The America, to the westward of the New Almaden 

 mine and a little south of the ridge, showed two small ore bodies. From 

 the plan of the drifts it would appear that clays running to the northeast 

 were followed. The Providentia, one quarter of a mile from the Enriquita, 

 in the direction of the New Almaden, yielded ore of excellent quality, as I 

 learn from Mr. Janin. The San Antonio mine was half a mile northwestward 

 from the Enriquita, on the hillside northeast of Los Capitancillos Creek, and 

 the San Mateo was a quarter of a mile farther in the same direction and 

 in a similar topographical position. 



A mass of black opal, such as is so often associated with cinnabar in 

 California, exists about 6,400 feet north magnetic from the Enriquita, be- 

 tween the isolated patch of rhyolite and the continuous dike. I am not 

 aware that cinnabar has been detected at this point, but it would not be 

 surprising if search were to disclose at least a trace of ore. 



Age and genesis of the deposits. — Tlic croppiuffs of Mluc Hill- havc becu exposcd 

 for a long time and there is a considerable quantity of cinnabar in the sur- 

 face soil of the hill. The deposits have been formed since any violent dis- 

 turbance of the country took place, however, for there are mere traces of 

 dislocation in the ore bodies. The eruption of rhyolite must have been 

 accompanied by very considerable movement of the country, and, had the 

 deposits existed before the formation of the dike, they could hardly have 

 escaped dislocation. There are no unquestionably Pliocene strata at New 

 Almaden, but beds of this age have been considerably disturbed both to 

 the north and to the south, though .at distances of a number of miles. It is 

 "very probable, but not certain, therefore, that the deposits are Post-Pliocene, 

 while it is certain that thev are not Pre-Pliocene. 



