294 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



made elsewhere on the structure of the Coast Ranges, lead me to believe 

 tliat the axis of upheaval at the close of the Neocomian coincided in direc- 

 tion with the present range, as was the case at later uplifts. In the area 

 mapped the various classes of metamorphosed rocks are so mingled that it 

 is not practicable, as at Knox\ ille and New Almaden, to lay down areas 

 which are chiefly serpentinoid. 



The serpentine near the county line contained a considerable quantity 

 of chromic iron, wdilch is said to have been mined at one time under the 

 belief that it was a silver ore. The workings are now so nearly obliterated 

 that nothing could be made out as to the character of the occurrence. As 

 is pointed out in Chapter III, particles of chromic iron are very common 

 in the serpentine of the Coast Ranges. 



The chico. — Resting against tlie metamorphic rocks are the Chico beds. 

 These are thousands of feet in thickness and the exposures are very 

 extensive, but the rocks are very poorly supplied with fossils. AVitli mucli 

 trouble, however, a small collection of fossils was gathered, and among 

 these Dr. White recognized Ammonites, BacuUtes, Inoceirtmus, and Lima 

 These genera are characteristic and the identifications are suflficient to 

 establish the age of the beds beyond a doubt. The rocks of this series are 

 for the most part soft, coarse, arcose sandstones of a reddish-gray tint; but 

 small quantities of shale, conglomerate, and limestone are here and there 

 intercalated between arenaceous beds. The prevalent rock is so soft that 

 branches of manzanita bushes, growing across croppings and sw\iyed by 

 winds, sometimes wear channels inches deep in the rock without being 

 killed. Near the mine, however, some induration has taken place, and 

 cinnabar has been deposited in the Chico sandstone. Seams of gypsum, 

 sometimes selenite, are common enougli in these beds, as well as in the 

 Tejon and Miocene strata. There are also at many points dark brownish- 

 red, spherical concretions in this sandstone which are vei'v firm. I do not 

 doubt that the induration of these masses has been effected by the action 

 of some substance which once existed at or near the centers. One of the 

 concretions from this locality was found to contain a fossil at the center, 

 and a few similar occurrences have been met with elsewhere. In Chapter 

 III, I have given the results of an investigation of one of the concretions 



