808 DESCRIPTIVE GEOLOGY. 



included within their border minute forms of nearly all the other mineral 

 constituents of the rock. 



This rock, from the northern end of the Truckee Eange, may be con- 

 sidered as typical of the hornblende-plagioclase-titanite granites, which are 

 so characteristic of the larger granitic bodies of Western Nevada, and both 

 lithologically and mineralogically stand so far removed from the great rock- 

 masses farther to the eastward, and from the smaller bodies of older gran- 

 ite which here and there crop out beneath the later variety. 



Dikes or narrow veins of quartz and finer-grained granite traverse 

 the coarser-grained rock of the Truckee Range in several places ; they are 

 frequently associated with massive black hornblende. 



Two or three miles to the northwest of the Truckee Range is situated 

 Hot Spring Butte, which properly belongs to the range, as it is only sepa- 

 rated by a low depression occupied by Quaternary beds. It forms a very 

 prominent landmark, rising over 1,000 feet above the plain, and derives its 

 name from the large boiling springs at its base, Avhich, from the earliest 

 days of emigrant travel to Northern California and Oregon, have been the 

 resort of camping-parties crossing the desert of the Mud Lakes. It is evi- 

 dent that it has been a favorite resort for Indians, and on the summit were 

 found large numbers of flint and obsidian arrow-heads and charms. 



At the northwest base of Luxor Peak occurs a re-entering basin in the 

 range, surrounded on nearly all sides by granite, but enclosed to the south- 

 west by Archaean schists and Tertiary basaltic rocks. The basin proper is 

 filled by sedimentarj- Tertiary beds, partially concealed by detrital material, 

 which have been referred to the Truckee Miocene, not, however, from any 

 direct evidence, but upon general grounds of more closely resembling the 

 uplifted beds that skirt the ranges than the horizontal Pliocene strata found 

 along the river-valleys. Stretching across the basin are beds of carbonate 

 of lime and gypsum, which, upon the north side, have been washed away by 

 the waters from the main canon of Luxor Peak, exposing a steep bank, 60 

 feet in height, of nearly pure white strata. The lowest stratum is a pearl- 

 colored limestone, of a coarse, saccharoidal, friable texture, overlaid by others 

 consisting of milky-white, fine-grained gypsum, carrying some minute crys- 

 tals of calcite, and forming the top of a broad ridge or bench. Rising out 



