MINES 



141 



cept for the Giant Powder-Ponce ore body, the ore 

 bodies were mined in slopes that trend N. 15-20 E., 

 and it can be safely assumed that the ores were local- 

 ized along swarms of hilos, which have this general 

 trend throughout the mine. The ore body mined in 

 the Giant Powder-Ponce stope, which was accessible 

 in 1945, lay along a relatively flat part of the west 

 flank of the extension of the anticline (pi. 5 and fig. 

 81), and even though the importance of the hilos is 

 not so obvious from the outlines of the stopes, the 

 hilos were found to be especially abundant in this 

 area. It is surprising that, although some explora- 

 tion has been done at the crest of the anticline to the 

 northeast of the Giant Powder stope along the pro- 

 jection of the hilos exposed in the stope, no ore has 

 been found there. (See pi. 4.) 



Suggestions for further development 



The margins of the sills in the area appear to have 

 been so completely explored that no sizable ore body 

 is likely to have remained unnoticed. Inasmuch as 

 the area has been reworked several times, it seems im- 

 probable that any very rich stope fill has been over- 

 looked. We feel, therefore, that even though this part 

 of the New Almaden mine could easily be made acces- 

 sible for mining it offers little incentive for further 

 development. 



NORTH RAND 01 AREA 

 Location and extent of workings 



The North Randol area surrounds what is known 

 as the North Randol ore body, which was the largest 

 single ore body developed in the New Almaden mine. 

 (See fig. 92.) This body trended a little west of 

 north, one end of it being about 450 feet southeast of 

 the Randol shaft and the other about 600 feet north 

 of it. From its apex near the 800 level it plunged 

 downward at an angle of about 50 to and below the 

 1800 level (pi. 4 and fig. 93). Access to the ore body 

 was afforded mainly by the Randol shaft, from which 

 levels extended at 100-foot intervals between the 800 

 and 1800 levels; and at greater depth the area was 

 explored down to the 2300 level by similarly spaced 

 workings connecting with the Santa Isabel and Buena 

 Vista shafts. In this area the deepest workings in the 

 New Almaden mine, reached through the underground 

 Church shaft, were driven on the 2450 level (643 feet 

 below sea level) to search for the downward extension 

 of the North Randol ores. Ore was trammed from the 

 Randol shaft at the 800 level to the surface through 

 the Randol tunnel, and at times some ore was also 

 taken out by a rather devious route connecting with 

 the 800-level Day tunnel. Several exploratory work- 

 ings that furnish geologic information in otherwise 

 unexplored areas are of special interest. These in- 



clude the 1100-level east drift, which reached a point 

 3,300 feet southeast of the shaft, the 1500-level cross- 

 cut extending 1,900 feet north of the Randol shaft, 

 and the 1800-level crosscut extending 1,100 feet south 

 of the shaft. (See pi. 4.) The aggregate length of 

 the workings in the North Randol area is more than 

 5 miles. 



History and production 



The development of the North Randol area began 

 in June 1871 with the sinking of the two-compartment 

 Randol shaft, which was absurdly inadequate in size, 

 being only 4 by 9 feet. At that time the ore bodies 

 of the central area had been followed northward and 

 downward to such a depth that the ore had to be back- 

 packed up to the 800 level and then trammed along 

 a circuitous route to reach the surface at the mouth of 

 the Day tunnel. The new Randol shaft was intended 

 to facilitate the handling of this ore lying to the 

 northwest and to explore its downward continuation. 

 For this purpose it was poorly located, but later, when 

 the North Randol ore body was found it proved to be 

 very advantageously placed. Because of the primi- 

 tive methods used in sinking the shaft, it had reached 

 a depth of only 383 feet by the end of 1871, and in 

 1872 it was sunk only 132 feet farther; in this year 

 drifts were being run, also, to the south and southwest 

 to tap the ore bodies on the 800 and 900 levels. Dur- 

 ing the next 5 years the shaft was slowly deepened, and 

 ore bodies lying to the west were sought and found on 

 several levels; however, little exploration was done in 

 other directions from the shaft. In 1877, 6 years after 

 the shaft was started, it struck "vein-rock" (silica- 

 carbonate rock) at a depth of only a little more than 

 700 feet, and a small amount of development work on 

 the 1200 level tapped the North Randol ore body. 

 (See section B-B', pi. 11.) Further exploration re- 

 vealed that this hitherto unknown ore body was very 

 extensive, and it lay close enough to the shaft to be 

 readily mined from the 800 level down to the 1800 

 level. By the end of 1880 most of the North Randol 

 ore body had been blocked out and was being mined. 

 In July 1882, in an attempt to explore the North 

 Randol area at still greater depth and also to over- 

 come the hoisting problem that resulted from the small 

 size of the Randol shaft, the large three-compartment 

 Buena Vista shaft was begun, about 1,600 feet north 

 of the Randol shaft. Workings driven southward 

 from the Buena Vista shaft explored the ore-bearing 

 structures at various levels down to the 2300, but they 

 revealed virtually no minable ore. As a result, the 

 magnificent and costly Buena Vista shaft, which was 

 sunk in 3 l / 2 years to a depth of almost 1,400 feet, was 

 never used for anything but exploration and pumping. 



