MINES 



133 



a bearing of a few degrees west of north to a point 

 above the 600 level, and the other shoot extends west 

 updip about half as far. As this body has been com- 

 pletely mined out, little is known of the character of 

 the ore; a few narrow dolomite-quartz veins, or hilos, 

 penetrate the walls of the exhausted stopes, but it 

 seems likely that the ore occurred largely as a blanket, 

 in which cinnabar filled small fractures and also ex- 

 tensively replaced the silica-carbonate rock. The lo- 

 calization of the shoots appears to have been controlled 

 by the shape of the hanging-wall contact, for the stopes 

 follow slight flexures nearly up the easterly dip of the 

 contact to above the 600 level. There the contact rolls 

 through a horizontal attitude to a westerly dip, caus- 

 ing the flexures to become domes. 



An unusual feature, not found in other accessible 

 parts of the New Almaden mine, is the extensive de- 

 velopment of a dolomite vein almost, but not exactly, 

 along the upper contact of the silica-carbonate rock. 

 This vein, which in places is more than 3 feet thick, 

 locally formed the back of several of the stopes be- 

 tween the 600 and 800 levels, but it probably follows 

 a postore fracture. Below the 800 level it grades in 

 places to a coarse dolomite-cemented breccia contain- 

 ing fragments of silica-carbonate rock, some of which 

 are largely replaced by cinnabar whereas others are 

 completely unmineralized. This mixture of mineral- 

 ized and unmineralized fragments is interpreted to 

 mean that the breccia and vein are younger than the 

 quicksilver mineralization. As the vein is straighter, 

 in both strike and dip, than the intrusive contact and 

 was taken as the hanging wall in mining, it seems 

 likely that in some places ore lying between the vein 

 and the overlying contact may have been missed. The 

 southern stope above the 700 level might be cited as 

 such a place, but, as the thickness between the vein 

 and the contact is small, no large amount of ore can 

 be expected to lie above the vein in this area. 



Suggestions for further development 



The compact area containing the Cora Blanca mine 

 appears to have been rather thoroughly explored. 

 The main ore shoots were bottomed, and extensive 

 deeper exploration along the ore-controlling contacts 

 indicates that for several hundred feet down their pro- 

 jected plunge there are no new shoots. To the north 

 of the well-explored area, however, some ore may have 

 been overlooked. The northernmost opening near the 

 600 level, known as the Water tunnel, exposed two 

 conspicuous northeast-trending zones of carbonate 

 veins, and the westernmost of these contains some fair 

 showings of cinnabar. These may represent "leakage" 

 above an ore body, as less conspicuous veins in other 



parts of the Cora Blanca area are believed to do, so 

 that exploration of the silica-carbonate rock lying di- 

 rectly underneath appears to offer promise of finding 



ore. 



HARRY AREA 



Location and extent or workings 



The Harry area, which contains the workings of the 

 "Harry mine," extends from near the Santa Maria 

 shaft southward to include the Yellow Kid opencut 

 on the east slope of Mine Hill. (See fig. 92 and pi. 3.) 

 Its principal drifts and crosscuts lie between the 800 

 and 400 levels and are about 13,000 feet in aggregate 

 length. Access to the levels was formerly gained 

 mainly through the Santa Maria and Harry shafts 

 and through the Harry, Yellow Kid, and Buzztail 

 adits; the workings are also connected on the 600 and 

 800 levels with the Cora Blanca workings to the east, 

 and on the 700 level with the central stope area of the 

 New Almaden mine to the west. The principal stopes 

 in the northern part of the workings lie between the 

 700 and 600 levels, those in the central part lie be- 

 tween the 600 and 500 levels, and those in the south- 

 ern part extend from the 500 level to the surface. 

 When the workings were being mapped for this re- 

 port, the 2 shafts, though partly open, could not be 

 descended, and the 800 level could not be reached. 



History and production 



The Harry ore bodies were not discovered until 

 1893, although they lay between the great central ore 

 bodies discovered in the early days of mining and the 

 Cora Blanca ore bodies, which had been known since 

 1873. In 1892, when the known ore bodies of the 

 New Almaden mine were nearing exhaustion and 

 funds for development were at a minimum, a new 

 small two-compartment shaft, known as the Santa 

 Maria, was begun just west of the main camp to ex- 

 plore the area surrounding the old rich Velasco ore 

 bodies. Early in 1893, while probing on the 600 level 

 for the downward continuation of these ore bodies, the 

 miners cut the north end of the extensive Harry ore 

 body, and, owing to the urgent need for additional 

 ore, the new find was quickly developed. When the 

 extent of this ore body had been determined, the 

 Harry shaft was sunk in order to remove the ores 

 more economically. Production began virtually with 

 the new discovery, and the Harry stopes furnished the 

 major source of newly mined ore in the New Almaden 

 mine for about 6 years. When the ore body was near- 

 ing exhaustion, the near-surface ores of the Buzztail 

 and Yellow Kid areas, to the south of the main Harry 

 ore body, were discovered, and these extended the pro- 

 ductive life of the Harry area for several years more. 



