228 IRVING. 



Red Path Creek Sheet and Laccolite. 



Toward the northwest from the summit of Twin Peaks, one 

 may see out on the Hmestone flat a low conical knoll. Ap- 

 proaching this over the intervening country, are found the flats 

 to be covered by talus of a dark basic hornblende-mica-diorite- 

 porphyry, whose chief component in weathered specimens 

 seems to be biotite. The rock is found sometimes in place, 

 and sometime only as a heavy talus. As one approaches the 

 knoll, the massive outcrops are more pronounced, the hill itself 

 being made up entirely of the rock. From this point it can be 

 traced far down into Red Path creek, which it finally crosses 

 in an abrupt cliff 



On the west bank of the latter creek the limestone dips away 

 from the porphyry at a high angle toward the west, but quickly 

 reassumes its normal inclination. This mica-diorite-porphyry 

 mass has spread out in great thickness and extent toward the 

 east, and appears to have split into sheets of varying size as one 

 proceeds in that direction. It outcrops on the crests of the 

 divides which run toward the northeast into Squaw creek, as far 

 as the west branch of Labrador gulch, and on the higher points 

 of these it is covered by thin cappings of Cambrian shales. 

 Just northwest of Twin Peaks it is cut by a dike of very coarse 

 tinguaite, the extension of which appears on the divide separat- 

 ing Red Path from Squaw creek proper. 



Bald Mountain. 



To the northwest of Terry peak rises the beautifully rounded 

 dome of Bald mountain, lying between the south fork of Dead- 

 wood creek on the north and the deeply carved Nevada gulch 

 on the south. The summit is covered by a considerable thick- 

 ness of a fine, bluish-looking quartz-aegirite-porphyry, and on 

 the side are exposed the Cambrian shales and quartzites. Many 

 faults occur on the mountain, and dikes, sheets and irregular 

 masses of quartz-porphyry and phonolite are extensively exposed. 

 It may prove to be the remnant of a laccolitic mass, but needs 

 further study. 



