374 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



decomposed basalt close to its contact Avith the sandstone. This dike is 

 typical, standing up as a ridge above the inclosing rocks and showing a 

 double columnar structure, one set of columns being transversely arranged, 

 while the other, at the croppings, is nearly vertical. The existence of these 

 superficial vertical columns shows that little erosion can have taken place 

 since the eruption of the rock. 



The ^'Etna property also comprises two other claims: the Washington, 

 containing alluvial deposits of cinnabar as well as native quicksilver along 

 clay seams, and the Pope claim, which contains a deposit of ciiuiabar in 

 contorted and silicified shales. The ^Etna mine is included in a belt com- 

 posed of serpentine, which can be followed almost without interruption as 

 far as St. Helena Creek, a distance of about seven miles. In this belt crop- 

 pings of opaline matter, which is largely opalized serpentine, form an almost 

 continuous ledge, with traces of cinnabar at many points. At one point, the 

 No. 2, or Phoenix No. 2, some work has been done. Mr. Luckiiardt describes 

 this mine as opened upon a layer of slate three to seven feet in Avidth and 

 carrving seams of ore of six to eight inches in width. The deposit seemed 

 unusually regular, but ore appears not to have been sufficiently abundant 

 to repay exploitation. 



All of the deposits mentioned above, as well as the veins of cinnabar 

 belonging to the Napa Consolidated Company, which have been described 

 in a previous chapter, are within three miles of the hot springs at Lidell 

 and within a triangular area measuring less than a square mile. Among 

 them are deposits in unaltered sandstone, in highly metamorphosed strata, 

 and in eruptive rocks. They embrace regular veins, impregnations, and re- 

 ticulated masses. Three of the deposits show unquestionable connection 

 with very recent volcanic activity, for one of them occurs in basalt, the 

 second is in contact with the same lava, and a very hot mineral spring flows 

 from the third. There is no reason to suppose that different genetic proc- 

 esses have been at work in this small area; on the contrary, there is every 

 reason to suppose that the deposits, embracing all the principal types of 

 occurrence, have been precipitated from waters heated by volcanic action, 

 in a manner similar to that by which the ores of Sulphur Bank and Steam. 

 boat Springs have been produced. 



