708 DESCKIPTIVE GEOLOGY. 



Underneatli this thick crust of crystalline salt is another layer of fine 

 saline mud and clay, also containing modified octahedrons of salt with clay 

 impurities. This second stratum of mud has not as yet been fathomed, and 

 it seems not at all improbable that there will be discovered other beds of 

 alkaline salts. It is to be regretted that no vertical section has been made 

 through the beds down to the Tertiary strata or underlying rocks, as it 

 would be of considerable geological value. Already very large quantities 

 of salt have been taken from this deposit to be used in the mills throughout 

 Western Nevada in the amalgamation of silver-ores ; but the field, if prop- 

 erly worked, is capable of furnishing immense amounts of nearly pure 

 chloride of sodium. 



Region north of Geanite Mountain. — North of Granite Mountain, 

 heavy beds of dark quartzite, having in general a westerly dip, rest uncon- 

 formably on the Archaean mass. They stretch northward for over 15 miles, 

 forming all the higher portions of the western side of the range, and, 

 wherever observed, extend down in broken, irregular ridges to the plain 

 below. At Spaulding's Pass, where the formation was crossed, the entrance 

 to the canon on the western side is through a narrow ridge of westerly- 

 dipping beds, which open out into a broad rolHng basin of quartzite hills, 

 presenting a somewhat uniform character in both topographical features and 

 Hthological habit. Many of the beds have a decidedly schistose structure, 

 in w^hich the individual quartz-grains appear flattened out into flakes and 

 pressed together in a compact mass, indicating a considerable amount of 

 metamorphism. The rock has a prevailing bluish steel-gray color, a con- 

 choidal fracture, and vitreous lustre. It is a dense, tough rock, breaking 

 with difficultj^ Lithologically it closely resembles the massive quartzite 

 formation of the Havallah Range, and without much doubt belongs to the 

 same geological horizon. It underlies the shales, limestones, and inter- 

 stratified metamorphic rocks in the north of the range, and has therefore 

 been referred provisionally to the lower quartzites of the Triassic age, which 

 form so marked a feature in the West Humboldt Range. Unfortunately 

 the point of contact with the Upper Triassic series to the north was not vis- 

 ited, and it cannot be definitely stated to underlie the latter beds conforma- 

 bly, the same doubt existing as was expressed in regard to the two forma- 



