TEUOKEE EANGE. 807 



ever the range was visited the evidence would seem to bear out such a 

 conclusion. A description of the physical outlines of this granite would be 

 simply a description of the range. It forms all the higher summits and 

 ridges, rising from 2,500 to 3,000 feet above the adjoining valleys, and 

 stretches across the entire width of the mountains until covered along the 

 base by the Quaternary deposits. In its lithological habit, in the details of 

 surface-outlines, and in mode of weathering, it bears the closest resemblance 

 to the rock-masses of the Granite Range, and is without doubt a part 

 of the same formation, only separated by the narrow desert of the Mud 

 Lakes. 



This granite is characterized by its great uniformity of texture. It is 

 medium-grained, with a fresh unaltered appearance, all the constituent 

 minerals being well developed, with frequently sharp crystalline faces. 

 Under the hammer, the rock breaks readily with an angular fracture. The 

 prevailing color is light gray, varying somewhat from light to dark shades 

 according to the amount of hornblende present. All structural lines seem 

 to be wanting, the rock showing no tendency to parallelism in the arrange- 

 ment of the minerals, even where the mica is present in considerable 

 amounts. 



Macroscopically the granite shows very clearly the following mineral 

 constituents: Quartz, orthoclase, plagioclase, biotite, hornblende, and titan- 

 ite. The quartz is well disseminated through the rock in limpid grains. 

 Plagioclase seems the much more abundant form of feldspar, and is char- 

 acterized by a brilliant lustre; both monoclinic and triclinic species are 

 white in color. Titanite may be easily recognized by its yellowish-brown 

 color, in small but perfect crystals. In addition to the minerals already 

 mentioned, Zirkel has detected, in a thin section from a typical specimen 

 found near the extreme northern end of the range, large numbers of micro- 

 scopical apatites and some minute grains of magnetite; the quartz-grains 

 are poor in fluid-inclusions. Professor Zirkel, in his report,^ gives, with 

 considerable detail, the microscopical analysis of this granite, presenting 

 some interesting observations on the structural features of the orthoclase 

 feldspars, and on the peculiar manner in which all the larger crystals have 



^ Microscopical Petrograpby, vol. vi, 40. 



