AURIFEROUS QUARTZ VEINS AND MINES OF GRASS VALLEY. 269 
from three inches to a foot or more, and in some parts of the mine several narrow veins com- 
bine and form a thickness of eighteen inches or two feet. This quartz is charged with veins of 
white iron pyrites bearing gold. An engine of fifteen or twenty-horse power drains the mine 
by a lift-pump, and raises the ore. 
It is difficult to find a mass of the quartz in which gold can be seen by the unassisted eye ; 
but on placing a lump of the pyrites in nitric acid for a short time, so as to partly dissolve it, 
gold becomes visible in numerous small points. A panful of the partly decomposed vein, near 
the surface, gives a good show of gold on being washed. When the quartz arrives at the mill, 
it is piled in heaps and roasted, and then passed through the stamps, of which there are sixteen ; 
the fine powder passes with a current of water, first over blankets spread out in the shallow 
troughs, and then through a long and slowly-revolving cylinder, partitioned off by cleats, and 
holding mercury, known as Cram’s cylinder. It is then received into a Blaisdell's pan—a large 
iron pan holding mercury and cannon balls—and kept in motion. Nearly three-quarters of all 
the gold is caught upon the blankets. These are ordinary blue blankets, and when they are 
taken out to be washed they present a most beautiful appearance, being covered with a layer of 
glittering particles.of gold. They are wrung out once every hour, into a large tub of water. 
The gold thus obtained is mixed with a portion of pyrites, and is subjected to amalgamation. 
This operation is performed weekly, and enormous ingots of gold are taken to the express offices 
every Saturday night. 
The Helvetia and Lafayette Mining Company is organized with a capital stock of $600,000, 
in shares of $100 each. "They have fine buildings and machinery, and a bank of eighteen 
stamps of great weight, and it is said that eighteen tons of the quartz can be crushed by nine 
of the stamps in twenty-four hours. The vein occurs in connexion with trappean rock, and 
trends nearly east and west, dipping a little east of north. A ridge of brecciated quartz rock 
Crops out in the low ground west of the workings, and has a trend nearly north and south. It 
is, perhaps, at the side of the intrusive rock. 
The specimens of auriferous quartz from this mine are exceedingly beautiful. The quartz is 
compact and milk-white, and contains implanted filaments and thin sheets of gold completely 
isolated from pyrites. Some ofthe specimens are exceedingly rich, and their remarkable solidity 
and freedom from the stains produced by the decomposition of pyrites, make them particularly 
suitable for cutting into ornamental stones. Pyrites is found in the quartz, and sometimes in 
cellular nodules, or lines cavities which contain gold. The wall of the vein, in some places, 
has a peculiar bluish-green color, and a layer of breccia is found. This consists of fragments of 
a silicious deposition, very compact, breaking with a conchoidal fracture, and yet without the 
brilliant vitreous lustre of quartz. It is deposited in layers of grayish-blue and white, and is 
hydrous, It is probably allied to cacholong, a variety of the species opal. Itis said that $12,000 
worth of gold was obtained from one hundred and thirty tons of the crushed quartz and earth of 
the upper or decomposed parts of the vein. This was crushed by nine stamps in eight days. 
Seven hundred dollars’ worth was once obtained from three and a half tons, being at the rate of _ 
$200 per ton. It is evident, from the appearance of the quartz, that the compact, undecomposed 
Portions will not give such a great yield. 
The Gold Hill mine is probably the most extensive at Grass Valley, and is under the super- 
intendence of Mr. Mellville Atwood. The entrance to the mine is at the base of the hill 
bordering the creek, and it is connected with the works for crushing and washing by a tram- 
Toad about nine hundred feet in length. The tunnel leading to the drifts upon the veins is 
