MINERAL RESOURCES. 689 



CHAPTER III. 



MINERAL RESOURCES AND IRRIGATION. 



It can not be denied, nor even doubted, that the mountain ranges and 

 mountain groups of Trans-Pecos Texas are continuations of those mountain 

 chains in Mexico and New Mexico where the mineral resources are partly 

 developed; their existence at least proved by numerous mines, prospects, and 

 outcrops. 



It also can not be doubted that the same forces which acted to build up 

 these mountains in Mexico and New Mexico were active in building up the 

 mountains of West Texas; that, judging from the petrographic character of the 

 rocks, our western mountains are similar, as a whole — we dare say, with local 

 modifications, identical — with those of Mexico and New Mexico; and that 

 therefore we are justified in supposing that the identity and similarity of the 

 character extends also to the ore bearing, even if we had not the actual proof 

 of the existence of valuable minerals by numerous outcrops, prospects, and 

 a few successfully worked mines. 



True, frequently it requires only slight modifications of the conditions or 

 of the character of the rock to change entirely the character of gangues and 

 veins, the investigation of smaller or larger districts; but we have some gen- 

 eral rules, based on the experience of centuries, by which we may determine 

 or at least suppose the possibility and probability of the ore bearing of rocks 

 and mountain ranges. Granites, syenitic rocks, amphibolite, diotite, green- 

 stone, and greenstone porphyries, as well as other porphyries, gneiss, mica 

 slates, talco slates, clay slates, some serpentinous rocks, crystalline limestones, 

 etc.. were centuries ago regarded as ore bearing rocks, and are regarded so 

 now. 



In the Quitman Mountains we find granite of evidently three ages in con- 

 tact with porphyritic rocks and crystalline limestones, greenstone, and ser- 

 pentinous rocks. In the Carrizo Mountains prevail talcose crystalline schists, 

 underlaid by granitic eruptive rocks related to those of the Quitman Moun- 

 tains. We find these schists and f eld spathic rocks under the Carboniferous 

 strata of the Eagle Flat cliffs, together with greenstone and serpentine 

 dykes; probably also under the cliffs of the Sierra Diabolo in their whole ex- 

 tent. The same crystalline schists and feldspathic rocks we find in the large 

 western spur of the Van Horn Mountains and in the valleys of the Van 

 Horn range, in the Eagle, Davis, Chinatti, and in the more eastern and 

 southeastern mountain ranges of West Texas; in the Ghisos, Corazones, Ro- 

 sillas, etc., mountains, with metamorphic and marbleized limestone, etc. We 



