FACTS IN AMERICAN MINING. 81 



of quartz in this country containing ounces of gold, and only 

 yielding pennyweights to the ordinary battery ; and this same 

 stone, if subjected to sufficient trituration, would. yield up ail, or 

 nearly all, its treasure. The ingenious apparatus of Messrs. 

 Lawson & Co. of Canterbury I look upon as eminently adapted 

 for the treatment of some kinds of gold-bearing stone. But it is 

 equally a mistake to use too fine a mesh for quartz containing 

 only coarse gold, there being an unnecessary loss of power and 

 time, without any corresponding gain. There is in fact no royal 

 road by which the tyro may attain perfection of work, — every 

 investigation points to the necessity of continuous and close 

 watching, and the exercise" of sound judgment, to meet changes as 

 they occur, to foresee and avert loss, to detect it as soon as it occurs, 

 and devise means of preventing its extension. In the stamper 

 battery used in California there is very little to note ; the stamps 

 range inVeightTrom 450 up to 1,500 lbs. ; the fall is 8 to 14 inches ; 

 speed, 32 to 80 blows per minute ; consumption of wood for every 

 10 tons of ore crushed, from less than one cord up to five cords ; 

 loss of mercury, never less than 7 lbs. for every 1,000 tons crushed, 

 and sometimes as much as 100 lbs. for the same quantity ; cost of 

 extraction, 8s. to £6 6s. per ton ; value of gold, 25s. to £20 per ton 

 of ore crushed — taken from one year's average in each case; cost 

 of stamping, from 2s. to 16s. per ton. In one mine the whole cost of 

 treatment was covered by 2s. 6d. per ton. Tn the stamping of 

 auriferous quartz it is not- an unusual thing to reckon that two- 

 thirds to three-fourths of the gold contents will be saved in the 

 battery. The calculation is made on the total quantity saved, and 

 certainly in the majority of cases no estimate is made of the gold 

 lost in the tailings. The amalgamating copper plates in this 

 country are often only 10 or 15 feet long, and frequently less ; and 

 some care is devoted to keeping them pretty clean, that they may 

 work well. In California they are often 100 feet long, and are 

 rarely cleaned, as they act much better when covered with gold. 

 These plates catch gold more or less all the way ; and although we 

 have no actual means of proving what quantity of gold is lost 

 after passing the short plates used in this country, we may reason- 

 ably conclude that some is lost which ought to be saved.* 



The quantity of mercury used has to be regulated as nearly as 

 possible by the quantity of gold it is expected to act upon ; as a 

 rule, 2\ to 3ozs. mercury should be used for every ounce of gold 

 supposed to be in the stone, but the appearance of the amalgam 

 is the best guide to an experienced eye. If too large a quantity 

 used, amalgam will be lost ; if not enough, it presents a rusty 



*In !N"ew Zealand there are several reefs where the tailings are worked to a great profit, 

 and many which without the reworking of the tailings would leave a loss instead of a profit. 

 The tailings from one mine alone were sold for £20,000, and it is alleged that the purchasers 

 profited largely ry the transaction, 



