802 DESCRIPTIVE GEOLOGY. 



biotite is less prominent, and the quartz occurs in larger grains, remarkably 

 clear and translucent. Under the microscope, the quartz is shown to be 

 very rich in liquid-inclusions. 



A characteristic feature of the mountains is the number of narrow 

 quartz veins, rarely over a few inches in width, which traverse the granite, 

 with here and there seams of fine-grained massive feldspar, with occasional 

 grains of quartz scattered through it. 



The slates already mentioned rest unconformably, at a high angle, upon 

 the granite, where they occur, both at the northern and southern end, as a 

 narrow belt of smooth, rounded hills between the crystalline rocks and the 

 Quaternary deposits. No structural or palseontological evidence of the age 

 of these slates was obtained, but, like the obscure outcrops of similar beds 

 between the Humboldt River and the Sierra Nevada, have been referred to 

 the Jurassic age. 



Between 5 and 6 miles to the southwest of the Pah-supp Mountains, and 

 connected with it by a low ridge nearly concealed by Quaternary accumu- 

 lations, occurs a small, isolated group of hills composed of granite and the 

 thinly-laminated Jurassic shales. The granite rises somewhat abruptly, 

 but barely attains an elevation of 1,500 feet above the surrounding desert, 

 extending in a north and south direction for about three miles. The chief 

 interest ^derived from this body of granite is the proof afforded of the 

 undoubted connection existing between the Pah-supp and Sah-wave Mount- 

 ains, the two groups forming a nearly continuous line of upheaval, with 

 low depressions barely covered by Quaternary beds. The granite of this 

 isolated mass was but little studied, and only visited at the extreme north- 

 ern end. It closely resembles, however, the rock from the Pah-supp 

 Mountains, with the same texture, mineral composition, and mode of 

 aiTangement. 



The overlying Jurassic beds extend eastward for 4 miles, nearly to 

 the Pah-tson Mountains, in low, undulating hills and obscure outcrops, the 

 surfaces of which are covered by loose fragments of extremely fissile gray 

 slates ; their relations to the rhyolites of the Pah-tson Mountains on the east 

 and the granites on the west are clearly indicated in the upper geological 

 section, at the base of Map V. These slates, which are highly metamor- 



