OCCUEREXGE OF CINXABAR. 257 



represents the pennanent level of the alkaline waters prior to the beginning 

 of mining operations. 



Occurrence of cinnabar. — The iTiode of occiuTence of cinnabar at the Sulphur 

 Bank is interesting and significant. It does not occur in sensible quanti- 

 ties at or close to the surfixce, but is- found to a considerable extent mixed 

 with sulphur in the lower portion of the zone of oxidation. The principal 

 deposits are below this level. They are found in the more or less decom- 

 posed basalt, in the underlying recent lake bottom, and in the Knoxville 

 shales and sandstones. The cinnabar is associated chiefly with silica, in 

 part crystalline and in part amorphous. In the lava it appears as small 

 seams, whicTi commonly follow either the original cracks between the blocks 

 or the concentric surfaces of the decomposed masses. In the lake deposits 

 below the basalt the cinnabar is found as impregnations oi- irregular seams. 

 In the workings from the Hermann shaft the ore occurs exactly as it does 

 in most of the quicksilver mines of California, more or less completely fill- 

 ing interstices in shattered rock masses. Sometimes ore of this kind has 

 been found which was simply a brecciated mass of rock cemented by cin- 

 nabar. The cinnabar in these cases has crystallized on the rock fragments, 

 exactly as quartz often does, and frequently leaves hollow inclosed spaces.' 

 To a small extent the more porous sandstones have been impregnated with 

 ore. Besides quartz, iron pyrites and marcasite frequently appear in the 

 gangue, calcite is not uncommonly also present, and small quantities of 

 bitumen are often found. It is a fact of great interest that Dr. Melville 

 has found small quantities of both gold and copper in the marcasite accom- 

 panying the cinnabar. The inferences to be drawn from the mode of oc- 

 currence of the cinnabar at this locality are not unimportant. The intimate 

 association of the ore with sulphur, opal, quartz, pyrite, and to a smaller 

 extent with calcite, is amply sufficient to show that it has been deposited 

 from water. This would also be clear if the cinnabar were not accom- 

 panied by and mixed with minerals which can have formed only in the 

 wet way. The vuggs lined with cinnabar and the relations of the veinlets 

 of ore to the fissure system of the rocks are of a character to convince any 



' See au illustratiou of such a specimen iu Le Conte anil Rising's paper on this locality (Am. Jour. 

 Sci., 3d series, vol. 24, 1882, p. 29). 

 MON XIII- 17 



