MINING. 275 
kinds of rock, are usually richer than those which have the 
same kind of rock on both sides. Thus it is said that the richest 
veins of auriferous quartz in California, have been discovered 
at the intersection of trap and serpentine, and the richest places 
in veins are where they cross from one kind of bed-rock 
into another. The richest part of a lode of auriferous quartz 
is almost invariably on the lower side of the vein, near the 
foot-wall. All these are facts to be remembered by the pro- 
spector as a guide, and an assistance to him in his search for 
a rich gold-bearing vein. If the lode is covered with earthy 
matter, he may sometimes trace its course by the difference in 
the color of the dirt and stones over it from that elsewhere. 
When the prospector finds dirt and stones on a vein, evidently 
disintegrated portions of it, he should wash some of the dirt 
in a pan, and if he finds no gold; there is a strong presumption 
that the vein is barren. 
§ 205. Prospecting Quartz Rock.—After finding a gold- 
bearing vein, the question arises whether it will pay. Great 
sums are lost in gold-mining countries by injudicious invest- 
ments in mills and machinery to work the auriferous rock, and 
persons going into the business should be particularly careful 
not to commit this great error. The business of quartz min- 
ing has great profits but also great pecuniary dangers con- 
nected with it. It is rarely that all the rock of a vein will 
pay for working. In some lodes, the vein-stone will average 
one hundred dollars to the ton, for all the stone found in a cer- 
tain part of the lode, but beyond that the rock may be poor 
or worthless. Picked specimens may be worth several thou- 
sand dollars to the ton, but perhaps not more than a ton of 
such specimens has been obtained in the best lode ever opened 
in the state. The most profitable lodes are those which have 
a large supply of rock, easily to be obtained, and all of it yielding 
something above the cost of working. The common method 
of ascertaining whether rock will pay, is to pulverize a little of 
it and wash it in a horn spoon. In taking out the quartz rock 
in large lodes, it is important to take out only that which will 
