MINERAL PRODUCTS. 21 



varying in width and character according to the geological conditions surrounding them ; 

 through this the river works its sinuous course, with a swift current and turbid water, till it 

 empties into the Colorado of the West. 



IV.— MINERAL PRODUCTIONS OF THE REGION OF COUNTRY, IN CONNEXION WITH THE MEXICAN 

 BOUNDARY LINE, FROM THE MEXICAN GULF COAST TO THE COLORADO OF THE WEST. 



[Note. — Tliis report was written before the treaty of 1853, and applies more particularly to the old boundary under the 

 treaty of Gaudalupe Hidalgo.] 



The mineral productions of the region of country, in connexion with the United States and 

 Mexican boundary line, are necessarily various, as corresponding to the different geological 

 formations. The detailed examinations necessary to furnish a satisfactory estimate of the real 

 value of this class of products are still wanting, and the peculiarities of the country itself place 

 great obstacles in the way of arriving at clear results. 



Among the most important, which we may here briefly enumerate, are: First. Such as are 

 connected with the various forms of igneous and metamorphic rocks, including Copper, Gold, 

 Silver. Second. Such as pertain to the stratified or alluvial deposites, including Coal, Salt, 

 Gypi^um. 



FIRST CLASS. 



Copper is quite frequently found in connexion with porphyritic rocks. The most usual form 

 of the ore is that of green malachite and red oxide. The locality best known is that of Santa 

 Bita del Cohre, which was profitably worked about 20 years ago. Analysis of ore from this 

 locality exhibited a yield of 75yVo P^r cent, of copper. — (See analysis by Professor T. Antisell.) 



No mine of copper is at present worked in any part of the region under examination. 



Gold is said to be sparingly found at various localities, in connexion with diluvial deposites, 

 derived from adjacent igneous rocks. It is here met with in a finely disseminated state, and 

 has never yet been found in sufficient quantities to yield a fair return for the labor expended. 

 It would seem here to belong to the same character of formation as that of Mexico, associated 

 with forms of porphyry, and never to approach in richness the deposits of California ; such, 

 indeed, we would expect in the general absence of metamorphic slates and quartz veins, so well 

 known to be the most prolific source of gold in other regions. But one locality of the true gold- 

 producing rocks was met with on our route, and that was at the furthest western point, near the 

 Pimo villages, on the Gila. — (Specimen rock, Nos. 97 and 98.) 



Silver. — Silver ore is found at several localities, mostly on the Mexican side of the line. It 

 has also been found in the Organ Mountains and various portions of southern New Mexico. 

 The localities best known in Mexico adjoining the boundary line occur at Corralitas and Presidio 

 del Norte, in the State of Chihuahua, and at Santa Eosa, in the State of Coahuila. The only 

 one at present successfully worked is that at Corralitas, before referred to. The ore from which 

 the silver is obtained is a form oi Argentiferous Galena, containing very variable proportions of 

 silver. According to the statement of the principal proprietor of these mines^ Mr. Flotte, the 

 average yield of the best mineral is 0.50 per cent, of silver ; analysis of a single specimen by 

 Professor Antisell gave only 0.03 of one per cent., a discrepancy difficult to account for, except 

 on the supposition that the ore varies remarkably in the relative amount of contained silver. 



