SURVEY OF COLORADO AND NEW MEXICO. 73 



Christo and on the south side of the Sierra Blanca Range, are prominent 

 terrace-like hills which are comx^osed of yellowish -brown maris and sands. 

 On the south side of the Sierra Blanca, they jut up high aud close on the 

 mountain slope. These marls are only remnants of large deposits which 

 once existed here, and spread out uniformly all over the valley. 



That there are mines of gold and other precious metals, as well as iron 

 and copper, in the mountains, along the eastern side of the San Luis 

 Valley, has long been known. Specimens of copper, indicating mines 

 of considerable richness, have been brought from the sources of the Cos- 

 tilla aud iron ores are scattered all over the valley of the Eio de las Uta s. In 

 the foot-hills of the mountains are fragments of magnetic iron ore, much 

 like that in the valley of the Chugwater Creek. Stray masses have been 

 traced up the mouDtain sides for about five miles, where a "blow-out" or 

 an immense mountain mass has been discovered. This iron occurs in the 

 gneissoid rocks, or what is called the Laurentian group, to which group, 

 I believe, all the gneissic and perhaps the entire mass of metamorphic 

 rocks of the Rocky Mountain system belong. I have assumed the posi- 

 tion, in all my investigations, that there are but two classes of changed 

 rocks in the West, viz, igneous and metamorphic, and that the oldest 

 granites which form the nuclei of the loftiest mountain ranges were once 

 aqueous rocks, deposited in the same manner as the limestones or sand- 

 stones of our most modern formations. It is on this ground that I have 

 so often used the terms '' changed" and " unchanged" rocks. By igneous 

 rocks, I always mean those only that I regard as having once been in a 

 fluid state, and may or may iiot have been protruded so as to reach the 

 surface. I also assume that these igneous rocks in the West may have 

 been thrust up at different geological periods, or at different times during 

 the same epoch. 



The gold mines near the Sangre de Christo Pass are the most import- 

 ant that have been discovered in the San Luis Valley. From some 

 notes kintll}^ furnished me by Dr. McClellan, United States Army, sur- 

 geon of the post at Fort Garland, the history of these mines appears to 

 be as follows: 



During the gold escitemeut in the San Juan Mountains, west of the 

 Rio Grande del IsTorte, in 1862, a large number of miners, or, as they 

 were called in tliose days, " pilgrims," crossed the Sangre de Christo 

 Pass, and camped for rest after a long journey from Idaho, Montana, and 

 ]!^orthern Colorado, on Placiere Creek, one of the main tributaries of 

 the Rio del Sangre de Christo. Learning from some passing Mexicans, 

 that in the olden time their people were accustomed to pack dirt from 

 some of the caiions of the mountains to the Placiere Creek, to wash out 

 the gold, they went to work and prospected the gulch of the Grayback 

 Creek. The San Juan excitement was, however, so strong that they 

 started to continue their journey the winter of the same year, many of 

 whom returned in a starving condition, and went to work in this gulch 

 with good results. 



In 1865 and 1866, Kit Carson with a x)arty prospected this region for 

 'placer diggings, aud took up many valuable claims. The gold taken 

 out by sluicing is very valuable and of a pure yellow color, and is what 

 is called "wire and scale" gold. It usually sells for about $19 per ounce 

 in gold, much more than the Morena gold or any other in this country. 

 A valuable lode with a well-defined cre^dce has been uncovered, but 

 little or no work has been done ou it. In the mountains at the sources 

 of the Rio Seco, on the west side of Culebra Peak, some lodes have been 

 found which apjiear favorable. Most of the foot-hills are covered with 

 beds of yellow marl inclining slightly. These foot-hills seem to be 



