332 MmmG industet. 



seams of calcspar and quartz ; the lime made from it in a limekiln, a few miles 

 north of Big Creek, is said to be of very poor quality. The general strike of 

 the body is north 35° east with a dip of 40° to the west, though the northern 

 end apparently partakes of the construction of the slates resting on the Aus- 

 tin granite. An immense seam or dike of quartz is found near the summit 

 of the ridge, above the limekiln, having a strike parallel to the general direc- 

 tion of the ridge, and corresponding in position to a quartzite dike near the 

 head of Ely's Canon. The occurrence of such dikes with a probable con- 

 tinuity for a long distance is one of the peculiar features in the geology of the 

 range. 



Directly east of Austin, forming the eastern water-shed of the Park Basin, 

 is a group of conical granite hills, having three principal peaks rising about 

 1,800 feet above the neighboring valley, called the Park Mountains. Their 

 entire mass appears to be of granite, which is in the main a compact, close- 

 grained variety, in which the feldspars predominate ; these are of two varieties, 

 a flesh-colored orthoclase and a greenish- white, probably oligoclase, besides 

 which the granite contains quartz and a magnesia mica, with some small green 

 crystals, probably hornblende. A narrow dike is observable on the slope 

 toward Park Creek, having a northwest trend, corresponding to that on the 

 east of Telegraph Pass ; the rock of this dike is a white granulite, containing 

 no mica, and the feldspar seeming partially kaolinized. 



On the north of the group the waters of the Park Basin have broken 

 through the granite body in a narrow gorge, in which the rock has been very 

 much decomposed by atmospheric agents, causing considerable accumulations 

 of granite sands in the ravines. The granite extends into the hills north of 

 this ravine for a short distance, and is succeeded by siliceous metamorphic 

 slates which rest upon it, dipping to the northward. The extensive flows of 

 rhyolite which form the table-topped ridges to the north and east, beyond the 

 limits of the map, probably extend to the flanks of these slates. 



Of the group of hills next south, lying to the north of Geneva, the 

 highest point, which rises about 3,000 feet above the valley, is of dark meta- 

 morphic slates similar to those of Telegraph Peak, succeeded to the north by 

 various fissile slates, whose debris form smooth slopes to the north and west. 

 These slates have a general strike somewhat east of north, and are traversed 



