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cavities, mixed with iron ocre, containing aurife- 

 rous pyrites and small grains of gold, some- 

 times, it is said, visible to the naked eye. It 

 appears, that the gneiss of the Cerro de Chacao 

 furnishes still another metallic deposite, a mix- 

 ture of copper and silver ores. This deposite 

 has been the object of works attempted with 

 great ignorance, by some Mexican miners, under 

 the superinten dance of Mr. A valo. The gallery * 

 directed to the North-East, is only twenty-five 

 toises long. We there found some fine speci- 

 mens of blue carbonated copper, mingled with 

 sulphat of barytes and quartz ;. but we could not 

 ourselves judge, whether the ore contained any 

 argentiferous fahlerz, and whether it occurred 

 in a" stratum, or, as the apothecary who was 

 our guide asserted, in real veins. This much is 

 certain, that the attempt at working the mine 

 cost more than twelve thousand piastres in two 

 years. It would no doubt have been more pru- 

 dent, to have resumed the works on the aurife- 

 rous stratum of the Real de Santa Barbara; 



contained, lie lior. 8 of the Frevberg compass, and dip 70 p to 

 the South- West. At a hundred toises distance from the au- 

 riferous quartz, the gneiss resumes it's ordinary situation, 

 hor, 3—4, with 60° dip to the North- West. A few strata 

 of gneiss abound in silvery mica, and contain, instead of gar- 

 nets, an immense quantity of small octaedrons of pyrites. 

 This silvery gneiss resembles that of the famous mine of 

 Himmelsfuerst, in Saxony. 

 * La Cueva de los Mexicanos. 



