SIMILARITY OF THE DErOSITS. 403 



used as medk-inal baths. Cinnabar was obtained tVoni the opening from 

 whicli the spring tiows. The other daims do not show especially elevated 

 tenn)eratures At the Starr claim cinnabar occurs at the contact between 

 a dike of basalt and the sandstone wall, the metal being found l)()t*i in the 

 decomposed lava and in the sedimentary rock. This mine has produced 

 5,000 flasks of quicksilver and is not exhausted. A second very similar 

 claim is the Silver Boiv, in which the greater part of the cinnabar is derived 

 from the decomposed basalt near the sandstone wall. There is no reason 

 to suppose that the eight productive deposits of this small area have been 

 produced by different methods or at essentially ditferent periods, and the 

 association of those mentioned above with hot sulphur springs and basalt is 

 sufficient evidence that the genesis of the deposits was substantially the same 

 as at Sulphur Bank. The minerals associated with cinnabar in the district 

 and the general characteristics of the ore are exactly the same as in the mines 

 to the south of San Francisco. 



Hot springs and cinnabar are also closely associated near Calistoga, and 

 the hot sulphur springs, miscalled geysers, in Sonoma County, lie within a 

 short distance of a number of small quicksilver mines. At Knoxville many 

 strong mineral springs are still depositing calcareous sinter, which in some 

 cases contains borax, but the water is no longer liot. In the Kedington 

 mine hot sulphurous gases are evolved at certain points and small amounts 

 of crystallized sulphur are being deposited. It is barely possible that in this 

 case some secondary action raises the temperature and induces the evolution 

 of sulphurous and sulphydric acids, but I was unable to detect any sufficient 

 cause for such action or any evidence that it was secondary. The pyrito 

 of this mine does not decompose readily, and the phenomena are confined 

 to a single portion of the mine, as they could scarcely be were this a case of 

 decomposition. Were the heat due to the oxidation of pyrite, the sulphydric 

 acid to the reduction of sulphates by timber, and the sulphurous acid to the 

 decomposition of sulphites or hyposulphites, one would expect to find the 

 phenomena repeated at other large mines, such as New Almaden and New 

 Idria; but they do not occur in those mines. The probabilities are thus all 

 in favor of the supposition that this is a veritable trace of a nearly extinct 

 solfatara. On the Manhattan claim near Knoxville a tunnel was run into 



