Geology of the Mother Lode gold belt. — Fairbanks. 215 
succession of strata occur ; first, chlorite schist, then six hundred 
feet of vein matter, containing three ledges of quartz besides 
several feldspathic dikes, west of this diabase, serpentine, diabase, 
decomposed rock probably once crystalline, slate, serpentine, slate, 
serpentine, and diorite. 
The greatest exposure of quartz is on the Mariposa grant in 
Bear valley. It is twenty feet thick and one hundred and fifty 
feet long at the base, rising eighty feet with a dip of sevent}' 
degrees. It presents a smooth, regular wall on its eastern face, 
but is somewhat cut up by longitudinal seams. 
In Mariposa county the lode is characterized hy two veins ; first, 
the one extending north from Princeton, through Bear valle}*, 
along the Merced river, and constituting the west vein at Coulter- 
ville. A break occurs in this vein between the Anderson mine 
and the Merced river. The other vein, beginning near the head 
of David's gulch, north of the Merced river, outcrops almost con- 
tinuously through Coulterville to Moccasin creek. The fissure 
continues into Tuolumne county, though containing but little 
quartz for a number of miles. It is widest at Quartz mountain, 
and here, as well as north and south for several miles, there are 
two veins, often lying side by side. In Calaveras county it is 
most prominent at Carson hill, Angel's camp, and in the vicinity 
of Mokelumne river. Through the centre of the county it is con- 
siderably scattered. Through Amador county it is nowhere 
confined to a single vein, but consists of a series of them, occupy- 
ing a width, at times, of nearly a mile. The same condition of 
things exists in El Dorado county. The veins are scattered 
through the strip of black slates, though the main vein usually 
occupies the eastern edge. 
Opportunity was not given for extended investigation into the 
mineralogical features of the lode for the reason that such a large 
number of the mines are not open. Professor Silliman, in an 
article in the Proceedings California Academy Science, III, 380, 
1867, has described several of the rarer metals, among them being 
tellurides of gold and silver, which are particularly abundant at 
Carson hill. He also gave the name mariposite, provisional^', to 
the green, scaly mineral which is so characteristic of the lode. 
This mineral is an anh\ r drous silicate, containing the bases — iron, 
alumina, chromium, lime, magnesia, potash, silicic and carbonic 
acids, and traces of manganese, and sulphuric acid. 
