104 KEMP'S GEE DEPOSITS. 



eruptive rocks (Example 37). Lake Valley, in Dona Ana County, 

 has been mentioned (2.08.04). In Lincoln County gold ores are 

 reported from the White Oak district. The principal mines of 

 Socorro County have been mentioned (Example 29), and the cop- 

 per in Permian sandstone under Example 21c. There are other 

 silver-bearing lodes in the Socorro Mountains near the town of 

 Socorro. Henrich has described (1. c.) a curious deposit of quartz 

 carrying gold and silver (the Slayback Lode) on the contact be- 

 tween the older bedded eruptions and a later siliceous dike in the 

 Mogollon range (Example 38). In Santa Fe County are impor- 

 tant placer mines (Example 44) and thin veins of galena in rhyo- 

 lite. In Bernalillo County are placers on the slopes of the Sandia 

 Mountains. In Colfax County, in the Rocky Mountains, are other 

 placers, and reported gold and silver mines.J 



COLORADO. 



2.09.09. Geology. The eastern portion contains prairies and is 

 a region lacking water. It consist of Quaternary and Creta- 

 ceous rocks. The plains rise in the foothills, which are chiefly up- 

 turned Jura-Triassic and Cretaceous strata. The Paleozoic is rela- 

 tively limited, although known. It rests on the crystalline rocks 

 of the Archaean. There are some minor uplifts, running out at right 

 angles to the Front range, that divide the foothill country into 

 basins, and are especially important . in connection with coal. 

 Next come the easterly ranges of the Rocky Mountains, in linear 

 north and south succession. They consist largely of dome-shaped 

 peaks of granite, with great local developments of volcanic rocks. 

 To the west follow the several parks, largely consisting of 

 Mesozoic strata. They are bounded by ranges again on the west, 

 some of which, like the Mosquito range (see under Example 30), 

 mark great lines of post-Cretaceous upheaval, and are accompanied 

 by immense igneous intrusions. On the east and west flanks of 

 the Sawatch range (the granitic Continental Divide) are Paleozoic 



1 W. P. Blake, "Gold in New Mexico," Proc. Bost. Soc. Nat. Hist., 

 VII., p. 16, July, 1859. "Observations on the Geology, etc., near Santa 

 Fe," A. A. A. S., X. 1859. S. F Emmons, Tenth Census, XIII., p. 101. 

 C. Henrich, "The Slayback Lode, New Mexico," Engineering and Mining 

 Journal, July 13, 1889, p. 27. R. E. Owen and E. T. Cox, Rep. on the 

 Mines of New Mexico, Washington, 1865. Rep. Director of the Mint, 1882, 

 p. 339. B. Silliman, " Mineral Resources of Southern New Mexico," M. E., 

 X. 424. Engineering and Mining Journal, Oct. 14 and 21, 1882, pp. 199, 212. 



