240 B, Silliman on the Grass Valley District. 
bon quartz.” This is especially distinct in the Norambagua, 
where, as before mentioned, the sulphurets are arsenical, and the 
gold very finely disseminated. He 
The average amount of gold in the Grass Valley veins is be- 
lieved to be considerably in excess of what is found in most 
other portions of California, In Allison Ranch, Massachusetts 
Hill, Rocky Bar, Ophir Hill, and Eureka, this average has prob- 
ably reached $50 to the ton. In many other mines it has been 
considerably less, but on the whole,-$80 may not be far from 
the general average for the whole district ; meaning of course, 
the amount actually saved by millin operations. 
The loss of gold is very various, but is probably nearly al- 
Ways greater than owners are willing to confess—if indeed they 
know, which is doubtful. It is certain, in one well known mine, 
my own samples of quartz sands, and sulphurets from ‘pans, 
assayed respectively $23 and $57 per ton—a result which was 
later confirmed, quite independently, by the researches of a very 
competent mining engineer. In other cases, as at Eureka and 
Norambagua, my own researches show the loss in the tailings 
be very small, not exceeding seven dollars to the ton in the 
latter, and less than that in the former. : 
e gold in many of the Grass Valley mines is very easily 
worked, being clean, angular and not very small, hence it 18 
co 
mills, mureurial riffes are placed in front of the discharge, but 
*y the whole body of crushed stuff is led at once oveF 
blankets, which are washed out every few minutes into 
where sme: fg gold and sulphurets are allowed to collect pre 
*_a¢e of an inclined table, over which the stuff is fed to the 
blad _sulated manner by a stream of water, while 170? 
»é = . Tevolve nthe vats to cause a sg te “ will 
. wcksilver, this a tus, at the Eureka ™ 
ninety per cent of all the cold is 0 elect wich is saved from 
Beyond the algamators, the sands are carried ove 
~ enatec’ copper sluices, and are put through various of 
