CARRIZO MOUNTAINS. 221 



about one mile east of the Bonanza mine. There the character of the rocks 

 changes from granite and feldspar porphyries into porphyries of augitic 

 character, and even to basaltic rocks. Intercalations and intrusions of green- 

 stone porphyries become more frequent, and leads with garnets (grossularite) 

 intermixed or in contact with sideritic iron crystals and quartz are of frequent 

 occurrence. 



Both of these ridges, as far as they have been examined, are crossed by 

 numerous vein outcrops and indications of ore, and wherever prospecting 

 holes have been sunk there are promising indications, and even distinct 

 veins of lead and copper-carrying silver, most of them having at least traces 

 of gold. Occasionally also tin is present. In the deeper strata these ores 

 are associated with zinc, which sometimes amounts to 30 per cent of the 

 whole; and even pure argentiferous zinc ores are found. In nearly all 

 prospects on the northeast slopes uranium is found in connection with the ore. 



The prospects on the north are mostly on contacts between granites and 

 porphyries; towards the river, on the southwest slope, on contacts between 

 porphyries or granites and crystalline limestone. Similar contact veins be- 

 tween porphyry and limestone exist in the Cretaceous hills west of Sierra 

 Blanca Station, which in all probability will yield good results when pros- 

 pected to greater depth, and may change to true fissures if granite or por- 

 phyry are reached. 



The outcrops of the Quitman Mountains are generally composed of iron 

 silicates, with probably some carbonate and oxide of iron, usually containing 

 a little silver; a few feet below the surface copperstain begins; deeper down 

 the quantity of copper increases, and traces of lead appear with the copper. 

 This becomes stronger the lower the shaft is sunk, and shows zinc and bis- 

 muth with the lead in greater depths. By using the pan, colors of gold are 

 frequently found in the gravel and sand; assays of quartz and ferruginous 

 material in many cases show at least traces of gold, particularly if such ma- 

 terial is taken from the vicinity of the greenstone porphyries. A small piece 

 of quartz found near Finlay assayed 1 1 ounces of gold to the ton. This and 

 the general character of the rocks establish the presence of gold in the Quit- 

 man Mountains, and probably in the Carrizo and other ranges, particularly 

 where the quartz runs with the greenstone porphyry, talcose schists, and gar- 

 nets. 



The Carrizo Mountains are composed principally of crystalline schistose 

 rocks, and although these disappear underneath the Carboniferous strata of 

 the Diablo foothills, the Carboniferous cliffs rest directly on micaceous and 

 talcose crystalline schists with numerous large veins of quartz. 



The dip of the rocks of the Carrizo Mountains and of the schists which un- 

 derlie the Carboniferous cliffs is southwest towards the Eagle Mountains. 



