I 922 ] Vaughan: Geology of San Bernardino Mountains 



349 



basic feldspar, and considerable quartz, although less than feldspar. 

 There is also some titanite, apatite, and a few rounded highly refrac- 

 tive, isotropic crystals, probably garnet. In a general way this descrip- 

 tion answers well for an igneous rock, but the field relations clearly 

 show that the rock is an altered sediment. One point worthy of note 

 is that the biotite does not show a strong tendency to cut across the 

 other minerals, but is usually between them. 



The ridge north of Ray wood Flat is of banded schist intruded by 

 granite. A specimen of the dark grey quartz-mica schist examined 

 under the microscope was found to contain a small amount of orthoclase 

 and albite-oligoclase and a few flakes of muscovite. Grains of magne- 

 tite and prisms of zircon and apatite are also present. On the ridge 

 to the southeast there are hornblende gneisses which are peculiar in 

 that they contain patches of hornblende less than a quarter of an inch 

 thick over areas four inches square. 



A large part of the schist along the south side of the mountains 

 has a ribbon-like appearance, as is well shown in Hathaway, Potrero, 

 and Millard canons. In the upper part of the latter, granite and 

 granite-gneiss predominate and are cut by pegmatite and aplite dikes. 

 Epidotization is common, pure epidote often being found in fissures 

 in the gneiss while in other cases the rock has been gradually replaced. 

 No large crystals of epidote were seen. East of Millard Canon the 

 schists and small areas of granite are intimately associated and fre- 

 quently the granite grades into distinctly schistose rock. The whole 

 mass is intruded by pegmatite dikes and on top of the main ridge west 

 of Deep Canon there are several transverse ridges of pegmatite made 

 prominent by differential erosion. Much of the granite is so decom- 

 posed that a pick can readily be driven into it and even some of the 

 pegmatite crumbles to a powder between the fingers. 



From Deep Canon to Whitewater River the schists are largely of 

 banded or ribbon-like varieties. In a general way they strike east and 

 west and dip 20° to the north, but locally dips may be found in any 

 direction. This can be seen in Stubby Canon, where the range of 

 strike is from N 45° W to N 50° E and the dip from 40° north to 

 20° south. On the west side of Whitewater River nearly vertical dips 

 are common. Here several quartz veins stained with limonite cut the 

 schist and some of them have been prospected for gold. Painted Hill 

 consists of schist striking N 30° E and dipping 30° N. Much of it is 

 badly altered and was probably mineralized, as it is now colored in 

 streaks with limonite and hematite, presenting the striking appearance 

 that gives the hill its name. 



