FUTURE PRODUCTION 



171 



years of production in the district. Even at such a 

 price, however, ore bodies similar to those that have 

 been mined in the past could be profitably mined un- 

 der present conditions, because technologic advance- 

 ments have appreciably increased mining efficiency 

 and lowered reduction costs. The average ore taken 

 from the New Almaden mine contained about 1 flask 

 of quicksilver per ton, or 4.0 percent, and the ore 

 from the Guadalupe mine was nearly as rich. Even 

 with quicksilver priced at only $70 per flask and min- 

 ing and reduction costs normal, 1 percent, ore can be 

 mined and furnaced at a profit ; and if large ore bod- 

 ies equal in grade to those that have been mined can 

 be found the margin of profit would allow consider- 

 able expenditure for further exploration. 



It also seems reasonable to expect that the price of 

 quicksilver will increase to its former high level at 

 some future date, owing either to the unavailability 

 of quicksilver from outside the United States or to 

 legislation. At such a time some of the submarginal 

 ore and dump material in the district could be treated, 

 even without spending money on further development 

 or exploration of the mines. In this way the district 

 can produce a small amount of quicksilver at times of 

 high prices with relatively small expenditure or risk. 

 But the district is believed to be equally capable of 

 yielding much larger returns on the greater expendi- 

 ture and risk involved in seeking new ore bodies. 

 Some places known or reported to contain submargi- 

 nal ore that could be mined at times of high prices 

 for quicksilver will now be pointed out, and an at- 

 tempt will then be made to show where new ore bodies 

 might be found along totally unexplored structures or 

 along unexplored parts of structures that contained 

 ore elsewhere. 



SUBMARGINAL ORE 



Known submarginal ore in the New Almaden dis- 

 trict consists of low-grade ore in place, stope fill, and 

 old dumps containing large tonnages of material re- 

 jected in the days of plenty. During World War II, 

 when quicksilver prices were high, such material pro- 

 vided a considerable part of the district's production. 

 At the New Almaden mine nearly all the known ac- 

 cessible stope fill and dump material containing more 

 than 2 pounds of quicksilver per ton was utilized, 

 and, at the Guadalupe mine, dumps sampled by the 

 U.S. Bureau of Mines (Bedford and Kicker, 1950, p. 

 5-9) proyided part of the ore treated in the rotary 

 furnace. 



Even larger amounts of stope fill and low-grade ore 

 in place are believed to remain in the now inaccessible 

 parts of the mines. This belief is based on the writ- 

 ten records of the mine superintendents or the known 



cutoff limit at the time when stopes became inacces- 

 sible. In general, however, this low-grade material is 

 so situated that it cannot be profitably removed, ex- 

 cept during a protracted period of exceptionally high 

 prices for quicksilver. 



Sampling of the landslide mass of silica-carbonate 

 rock breccia near the Kelly cuts of the Guadalupe 

 mine (pi. 14) is reported (Bedford and Ricker, 1950, 

 p. 5-9) by the U.S. Bureau of Mines to have indicated 

 34,400 tons of ore containing 2.33 pounds of quick- 

 silver per ton, on the conservative assumption that the 

 deposit is only 10 feet deep. This is equivalent to a 

 little more than 1,000 flasks of quicksilver. Some of 

 the richest ore in this landslide was taken out, how- 

 ever, after the sampling was done. Sampling of most 

 of the dumps in the Guadalupe area indicated 56,480 

 tons of ore containing 2.26 pounds of quicksilver per 

 ton, equivalent to 1,680 flasks of quicksilver. Some 

 rock impregnated with mercury is also known to re- 

 main beneath the old brick furnaces on the Guada- 

 lupe property, but its grade and quantity are not 

 known. The Thayer and Dore Labores in the old 

 Guadalupe mine were last reworked in 1884 and 

 doubtless contain stope fill that could now be profit- 

 ably treated, but to gain access to this material and 

 mine it would be very costly. 



The possibilities for finding submarginal ore in the 

 various "outside" mines of the New Almaden property 

 may be briefly considered from west to east. The 

 Senator mine dumps have been partly reworked by 

 lessees making use of screens and hand sorting, but 

 this material appears to be too low in grade to be 

 considered even as submarginal ore. No other readily 

 accessible submarginal ore in the Senator mine area 

 is known. The San Antonio mine was reported by 

 one of the early mine superintendents to contain a 

 large block of "low grade ore," but according to C. N. 

 Schuette, who has examined this mine in recent years, 

 this material is of too low grade to be of value in the 

 foreseeable future. The Enriquita mine dumps have 

 been largely reworked and probably contain little of 

 value; it is reported, however, that the old stopes lying 

 above the Eldredge tunnel (fig. 96) may contain good 

 furnace ore. 



In the New Almaden mine area most of the dumps 

 containing more than 2 pounds of quicksilver per ton 

 have already been reworked, though some parts of the 

 large dumps at the portals of the Day and Randol 

 tunnels may have been missed. Some low-grade ore in 

 place may yet be obtained from the big surface cuts 

 to the south of Mine Hill, where the recent operation 

 was abandoned largely because of the drop in the 

 price of quicksilver; and some could probably be 



