354 University of California Publications in Geology [Vol. 13 



with parts of the Arrastre quartzite farther northwest and its general 

 relations to the limestone are identical, it is believed to be a part of the 

 same formation. 



There is a strip of quartzite sunken into granite and striking 

 N 30° E along the hills north of Antelope Canon three miles southwest 

 of Saddleroek Spring. It is massive and rather pure, though it con- 

 tains occasional grains of magnetite and flakes of biotite. Other areas 

 of altered sediments are similarly sunken in the granite to the north 

 and northeast and all may be remnants of the Arrastre quartzite. This 

 may also be the case with some of the undifferentiated schists on the 

 south side of the range, but, as blocks of the Saragossa quartzite might 

 be isolated in a similar manner, positive identification is impossible. 



The Arrastre quartzites have undergone considerable metamorph- 

 ism since their original deposition as sandstones, and portions con- 

 taining impurities show this particularly well. A medium fine-grained 

 grey quartzose schist from Rattlesnake Canon, just below Mound 

 Spring, appeared under the microscope to be practically free from 

 feldspar, only a very small amount of orthoclase and a few grains of 

 plagioclase, probably oligoclase, being present. Some of the quartz 

 occurs as a fine aggregate as if secondary. The quartz and feldspar 

 show undulatory extinction. The rock contains a large amount of 

 biotite as scattered flakes and in small aggregates. There is consid- 

 erable muscovite with the biotite and both are often bent. Numerous 

 small hairlike tufts of a colorless mineral are present, usually associ- 

 ated witli the biotite. Its optical properties could not be definitely 

 determined, but the occurrence and general form suggests tourmaline. 

 There are a few small grains of titanite, and a small amount of green 

 hornblende is seen going over to a colorless amphibole. 



A fine-grained grey quartzite from Rattlesnake Canon three and 

 a half miles below the branch to Viscera Spring was found to consist 

 almost wholly of small quartz grains interlocked by secondary addi- 

 tions to the original fragments. Numerous fine flakes of biotite, a few 

 flakes of muscovite, and many small grains of magnetite are also 

 present. 



On the north face of the range the qur.rtzite is rather impure. A 

 specimen from a mile and a quarter east of the mouth of Arrastre 

 Creek is a fine-grained schistose rock mostly yellowish-white in color 

 but with discontinuous dark streaks high in biotite, the flakes being 

 arranged parallel to the schistosity. It is largely composed of quartz 

 grains elongated in the same direction. A little orthoclase is present, 

 but no plagioclase ; also a little titanite and a few grains of magnetite. 



