n the bowl is continually moving; and the bottom is divided
by little compartments, which make a constant riffle. In other bowls
the pulverized quartz is forced with water through the mercury. The
methods of amalgamation differ very much, and a book might be filled
with a description and discussion of the processes used at different
quartz-mills in California.

_Sulphurets._--Many auriferous quartz veins contain considerable
quantities of sulphurets or pyrites of iron, copper and lead, and their
presence prevents amalgamation, and thus causes a great loss of gold.
It is said that on some occasions in good mills, not more than twenty
or thirty dollars have been obtained from a ton of vein-stone which had
seven or eight hundred dollars of gold in every ton. The best method of
treating the quartz containing pyrites, is to roast it, and thus drive
off the sulphur, but this process is so expensive that it is seldom
used; and the common practice is to crush and amalgamate the rock, and
save the concentrated tailings for some future time, when there may be
a sale for them, or when it will be cheaper to reduce them. The
pulverized sulphurets are decomposed by exposure to the air, and after
the tailings have been preserved for a time, they may pay better at the
second amalgamation than at the first. A mixture of common salt assists
the decomposition of the pyrites.

_Chief Quartz-Mills._--The most productive quartz-mill in the state is
the Benton mill, on Fremont's Ranch, in Mariposa county. It is also the
largest, having forty-eight stamps. There are four mills on the estate,
with ninety-one stamps in all, and their average yield per month is
sixty thousand dollars. A railroad four miles long, conveys the quartz
from the lode to the mills. The Allison quartz mine in Nevada county,
produces forty thousand dollars per month. The Sierra Buttes
quartz-mill, twelve miles from Downieville, yields about fifteen
thousand dollars per month. These last mills run night and day, and
crush and amalgamate ten thousand tons of rock a year, or twenty-eight
tons per day. Forty men are employed, twenty-five to quarry the rock,
five in the mill to attend to the stamps and amalgamation, one to do
carpentry, one for blacksmithing, and eight for getting out timber,
transporting quartz, and so forth. The cost of quarrying, crushing and
amalgamating a ton of rock, is six dollars. The wages of the men are
from fifty to seventy dollars per month with b