356 Whitney’s Geology of California. 
continue in the direction of N. 54° W. 
he slates on each portion are remarkably parallel, and have 
every possible degree of metamorphism, and in places have 
sandstones interstratified with them. They dip at all angles, but 
always to the east. 
uartz veins are very numerous, and generally have the 
same direction as the strike of the slates, or very near 1t. 
strata again change the direction of their strike 26°, and then 
We. 
average breadth of the quartz is fully twelve feet, and - places 
it expands to forty feet, all of solid vein-stone. As with most 
uncertain. The processes of extraction, however, have 
always been the best, or the most economical. t 
rinceton mine, six miles southeast of the mines - 
named, is the most extensive, and has yielded the most gol , 
he works extend to over 500 feet in depth, and over 1400 o 
in length, and the yield is stated to have been about $2,000,000. 
But we cannot enter into further details. : a 
It was near the Pine Tree mine that Mr. King discovered, 
first in Jan. 1864, those Jurassic fossils which indicated unmis- 
takably the age of these slates. Some of them were foun 
within a few feet of the vein. h 
line of very heavy outcrops of quartz commences at 
Pine Tree and Josephine mines and extends northwest neary 
70 miles to Jackson, in Amador county. Many persons have 
supposed this to be one vein. If it cannot be proved that these 
In Mariposa county there are scarcely any of those superficial 
volcanic accumulations that so modify the mining features 
the northwest. Hence, there aré few or no “deep diggings” 
great hydraulic washings; the placers are more shallow, 224, 98 
@ consequence, sooner exhausted. 
