450 



Report of the State Geologist. 



the walls of the ore-body. Orthoclase feldspar abounds. The rocks around 

 the ore-bed have been much sheared and strained, but no actual faults were 

 found on the surface. One of the specimens showed a breccia of feldspar 

 and magnetite. One mile northeast of the Oregon mine, the grey gneiss 

 again appears, being a mixture of quartz, feldspar and biotite. It dips 4<>^' E. 



Along the road leading from Greenwood lake to Tuxedo and in the area 

 due north of Sterling lake, the gneiss is, at times, very massive, with red 

 feldspar, and resembles granite. Just northeast of the cross-roads, on the 

 road to Southtield (305), the rock is a massive, red, feldspathic gneiss with 

 some quartz and much garnet. It strikes N. 20° E. and. dips 70° S. E. 

 Little or no mica is present. 



This may be only a local variation, for about a mile and one-half farther 

 to the north the common grey gneiss again appears, striking N. 25° E. and 

 dipping 40° E. The strike is, however, very variable. 



From Southtield Works to Helmsburg, south of Mount Basha lake, the 

 gneiss preserves a remarkably constant character. It is fine-grained, light 

 grey, strongly laminated and composed of quartz, orthoclase feldspar ami 

 biotite. Some plagioclase is present, and hornblende is not uncommon. The 

 strike near Southtield Works is X. 40° E., dip 60° S. E. Farther to the east, 

 along the road, it is N. 20° E., dip 60 c> S. E. At this point the gneiss 

 sometimes contains dark bands of more basic rock, which in appearance 

 resembles the gneiss around Sterling lake. 



Much of the gneiss in Tuxedo park is fine-grained and very basic, that at 

 the southern end of the park, especially, containing considerable quantities of 

 pyroxene, with strong basal parting. The dip is nearly always to the east. 

 Along the Switchback road, near the summit of the hill and at a point about 

 330 feet higher than Tuxedo station, there are numerous veins of a coarse red 

 granite identical with that found near Stockbridge's hotel, east of Central 

 Valley. 



On the circuit road within Tuxedo park there are many exposures of a 

 well lianded grey gneiss with alternating light bands of quartz and feldspar 

 and dark ones of hornblende, w ith some biotite. The gneiss strikes N. 40° 

 E. and dips 50° S. E. 



One mile before reaching the north gate and on the circuit road, are 

 large outcrops of an extremely coarse dioritic rock, similar to one southeast of 

 Southtield. It is much coarser, however, and contains some quartz. In close 

 association w ith it is a fine-grained granular gneiss ami stringers of the diorite 

 often penetrate it. 



