GREAT EASTKltX AND (illKAT WKSTKltN MINES. 375 



The next deposit to the north of tlie Pope Valley group of mines is 

 the Great Eastern, ni Lake ('uunty, on 8t. Helena Creek.' This deposit 

 was remarkable for the riehness of its ores, Init tlie (piantlty of (piicksilver 

 produced was small and the mine has been abandoned for several years. 

 The specimens obtained from the dumps show that the ore was accompanied 

 by opaline rock and that an oil was present, associated with dolomite. A 

 large amount of unaltered sandstone on the dumps suggests a wall of this 

 rock.. Just northeast of this claim, on the opposite side of tlie creek, is 

 Bradford's Prospect, in whieli also the cinnabar is associated with opal. 

 Difficidt drainage, due to the proximity of the creek, is said to have inter- 

 fered with the development of this deposit. Tt is stated that since I visited 

 this locality a shaft has been sunk and that a considerable ore body has 

 been developed. 



The next deposit to the northwest is the Great Western, described in 

 detail in the preceding chapter. The district between the Great Western 

 and Pine Mountain has been actively prospected, and nnxny claims have 

 been taken up and again abandoned. It is not possible to get much infor- 

 mation about these deposits, none of which has been extensively developed 

 and in none of which extensive ore bodies were found. The AVall Street is 

 on a laver of opaline, metamorphic rock. Glaucophane schists occur In this 

 mine and it was in specimens from this locality that glaucophane was lirst 

 detected in California. Native quicksilver existed here as well as cinnabar. 

 The American mine was located upon a ledge of indurated strata which 

 form croppings of considerable height. The rock consisted of alternating 

 beds of sandstone, siliceous slate, and partially serpentinized sandstone, and 

 underlying the ore-bearing strata was dense serpentine. The cinnabar 

 sometimes impregnated disintegrated and ocherous material, but was mostly 

 found in seams and bunches in the siliceous rocks. Quicksilver, pyrite, and 

 bitumen accompanied the cinnabar. The deposit appears to have been an 

 impregnated series of strata and the ground nuist have been charged with 

 ore after the metamorphism of the rock.= According to Mr. D. de Cortazar* 

 specimens containing selenide of mercury were obtained from this mine. 



I A more important mine of the same name in Sononn County has been described in the preceding 

 chapter. 



- Uupnblished report of L. Janin. 



^Uritish Reports on Ihr lMii1:i(lcl|ihia Int. rnatinnal Ex]i(isilinn of IHTIi, vol. :!. 



