MINES 



155 



rocks that are so thin they are not indicated in the 

 notes and maps available to us. 



Ore toodles 



The ores of the Enriquita mine are similar to those 

 of the nearby New Almaden mine, in that they contain 

 cinnabar both replacing silica-carbonate rock and fill- 

 ing open fractures. Two large ore bodies and several 

 smaller ones extended through the central part of the 

 altered sill forming a gentle arch 550 feet long and 

 from 15 to 40 feet wide. This arch has an altitude 

 of less than 750 feet in the northwestern part of the 

 mine, rises to 980 feet in the central part, and sinks 

 to 700 feet in the southern part. In all probability, 

 however, the ore bodies did not lie along a single 

 structure; as they are near the middle of the sill, it 

 is likely that they bordered several steeply dipping 

 septa of sedimentary rock. Their trend is such as 

 to indicate that they are unrelated to the hilos, which, 

 according to Christy 10 "cross the silica-carbonate rock 

 of the Eldredge tunnel in a nearly north and south 

 direction." 



Suggestions for furtner development 



The Enriquita mine does not thoroughly explore the 

 carbonatized sill below the Main tunnel level, except 

 along the northern margin on the 400 level ; but until 



i" Christy, S. B., 1889, Unpublished report to the Quicksilver Mining 

 Co. 



the geology is more precisely known it will not be 

 possible to judge whether more ore is likely to be 

 found in the mine. Because of the unusually steep 

 slope of the surface, together with the availability 

 of the Eldredge tunnel and the many reported occur- 

 rences of veinlets of cinnabar, especially along the 

 northern contact, the mine might have considerable 

 promise for low-cost mining of low-grade ore if a fur- 

 nace were built near its portal. 



SAN ANTONIO MINE 

 Location and extent ol workings 



The San Antonio mine lies on the south slope of 

 the Los Capitancillos Ridge, a few hundred feet up- 

 stream from the Guadalupe Dam and about 2,000 feet 

 northwest of the Enriquita mine. (See pi. 1.) The 

 lowest workings, which are not far above the floor of 

 Guadalupe Canyon, are flooded with water impounded 

 by the dam, and they lie in part under land that is 

 no longer a part of the New Almaden property. The 

 more recent workings consist of two adits, known as 

 the Upper and Lower San Antonio tunnels, driven 

 northward into the ridge; a somewhat older short 

 adit lies higher up the ridge. (See fig. 97.) Still 

 older workings are said to have been driven in the 

 very early days, but if they exist they are caved, and 

 in 1948 they could not be found. As they apparently 

 were never mapped, we have no information about 

 their location or extent. 



Old workings 



EXPLANATION 



Upper Miocene 

 or Pliocene 



KJs 



Ore, up to 7 Ib 

 Hg per ton 



Upper Jurassic to 

 Upper Cretaceous 



Sedimentary rocks of 

 the Franciscan group > 



540 ft 



DATUM IS MEAN SEA LEVEL 



Contact, showing 

 direction of dip 



Inferred contact 



200 FEET 



TERTIARY 



JURASSIC, 

 CRETACEOUS, 

 AND YOUNGER 



JURASSIC AND 

 CRETACEOUS 



All workings and notes from mining company records 



FIGURE 97. Geologic map of the more recent workings of the San Antonio mine. 



