. AGATE PASS llEGION. 573 



mentary formations, nor were fossils obtained. As heavy beds of qnartzite 

 and overlying limestone to the north of Agate Pass have been placed in the 

 Weber Quartzite and Upper Coal-Measure limestone, the Tenabo Peak beds 

 have also been provisionally referred to the horizon of the Upper Coal- 

 Measures. 



In the canon through which the road passes, just north of Shoshone 

 Wells, an isolated patch of limestone is found, also resting upon the granite, 

 and dipping at a high angle to the northward, but which has not been indi- 

 cated on the map. 



In the Tenabo Peak limestone are a number of well-defined mineral 

 veins, many of them- having been extensively worked. The ores are rich 

 in silver sulphurets, but combined with zinc, lead, and other base metals, 

 requiring expensive metallurgic.al processes. A description of the Cortez 

 Mining District will be found in "Mining Industry".^ 



Agate Pass E,EGiON.^^-The Agate Pass depression trends northwest and 

 southeast at right angles to the general course of the range. The western 

 foot-hills of the range south of its mouth are formed of heavy-bedded dark- 

 l)lue limestones, which are locally more or less changed into marbles and 

 invariably crystalline, and, as far as observed, contain no fossils. They 

 have a strike a little east of north, dipping eastward, or toward the caiion. 

 The thickness exposed may be 1,200 or 1,500 feet. On the eastern edge 

 of their outcrop, they abut against a mass of diorite, which fills the bot- 

 tom of the canon for several miles, and extends northward, occupying the 

 northwest foot-hills of the range for about 4 miles. This diorite is highly 

 crystalline rock, containing very little groundmass, and is composed of well- 

 preserved triclinic feldspar, green hornblende, abundant quartz, and a high 

 proportion of brow*n biotite, but, as far as observed, no apatite. The crys- 

 tals of triclinic feldspar are in some instances a quarter of an inch long, and 

 the hornblendes sometimes reach an eighth of an inch in length. The feld- 

 spars are more or less impurified by small inclusions of hornblende and 

 mica, while the quartz crystals in general seem quite free from them. 



^Miuing Industry, vol. iii, 405. 

 *From field-notes of Clarence King. 



