SILVER AND GOLD. 203 



nate north and south ranges of mountains are found, which are 

 less elevated than those of Colorado. The Colorado ranges vir- 

 tually die out at the northern boundary. The northwestern por- 

 tion comes in the great Colorado Plateau, and has been quite 

 fully described by Captain Dutton (Eighth Ann. Rep. Director 

 IT. S. Geol. Survey}. In numerous localities throughout the 

 Territory volcanic action has been rife and in places is but re- 

 cently extinct. The eastern part is largely Cretaceous, and also 

 the northeastern plateau, which contains much valuable coal. The 

 mountain ranges often have nuclei of Archaean crystalline rocks, 

 with successive strata of Carboniferous, Permian, Triassic, Juras- 

 sic, and Cretaceous on the flanks. The mining regions are in 

 these ranges of mountains. 1 



2.09.08. The southwestern county is Grant, whose lead-silver 

 deposits have been briefly referred to. North of Silver City are 

 quartz veins of gold and silver ores, in diabase and quartz por- 

 phyry (Example 37), and again, west of Silver City, are ferru- 

 ginous deposits with chlorides and sulphides of silver in limestone. 

 In the Burro Mountains are silver ores in limestones, apparently 

 Lower Silurian. The Santa Rita Mountains contain, in addition 

 to the copper (Example 20c7), silver and gold in quartz veins in 



1 W. P. Blake, Proc. Bost. Soc. Nat. Hist., 1859, Vol. VII., p. 64 

 " Geology of the Rocky Mountains in the Vicinity of Santa Fe," A. A. A. S., 

 1859. A. R. Conkling, "Report on Certain Foothills in Northern New 

 Mexico," Wheeler's Survey, Rep. of Chief of U. S. Engineers, 1877, II. 1298. 

 E. D. Cope, " Report on the Geology of a Part of New Mexico,'' Wheeler's 

 Survey, 1875 ; Appendix Gl. C. E. Dutton, "Mount Taylor and the Zuni 

 Plateau," Sixth Ann. Rep. U. S. Geol. Survey, pp. 111-205. S. F. Emmons, 

 Tenth Census, Vol. XIII. 100. O. Loew, "Report on the Geology and 

 Mineralogy of Colorado and New Mexico," Wheeler's Survey, 1875 ; Ap- 

 pendix G2, p. 27. J. Marcou, "The Mesozoic Series of New Mexico," 

 Amer. Geol., IV. 155, 216. R. E. Owen and E. J. Cox, "Report on the 

 Mines of New Mexico," Washington, 1865, 60 pp., Amer. Jour. Sci., ii., 

 XL. 391. G. F. Runton, " On the Volcanic Rocks of New Mexico," Quar. 

 Jour. Geol. Soc., Vol. VI., p. 251, 1850. B. Silliman, Jr., "The Mineral 

 Regions of Southern New Mexico," M. E., X. 434. F. Springer, "Occur- 

 rence of the Lower Burlington Limestone in New Mexico," Amer. Jour. 

 Sci., iii., XXVII. 97. J. J. Stevenson, "Geological Examinations in 

 Southern Colorado and Northern New Mexico," Wheeler's Survey, 1881. 

 " Geology of Galisteo Creek," Amer. Jour. Sci., iii., XVIII. 471. " On the 

 Laramie Group of Southern New Mexico," Amer. Jour. Sci., iii., XXII. 

 370. 



