TAYLOR'S GEOLOGICAL RECONNOISSANCE. 83 



So far as our opportunities of investigation permitted, it appeared very certain that 

 numerous modifications of the porphyritic rocks exist on the Isthmus. In the cases 

 alluded to, the base of the series was always occupied by the more compact variety. 

 In the black trap of Point Palenque, there prevails several horizontal courses of 

 ferruginous nodules. The neighboring Point of Escribanos exhibits a corresponding 

 series of this ferruginous trap, associated with a beautiful bronze or dark green 

 porphyry, not much unlike to that of Egypt. Surmounting the harder beds of rock 

 are seen others of highly ferruginous trappite, whose decomposed surfaces are 

 recognised at a great distance, by their bright red color. 



Minute grains and crystals of black magnetic iron sand are washed upon the beach, 

 and are accumulated at every tide near Escribanos. 



In the gold district now under our consideration, the range of the strata is about 

 east and west, or a little south of west, thus conforming to the local bearing of the 

 coast, hereabouts. These stratified masses or beds are, in general, arranged in a 

 vertical position. Those beds which enclose auriferous quartz veins appear to be 

 universally at a very high angle. 



Under the comprehensive term " metalliferous porphyry," the Spanish geologists 

 comprise a numerous suit of rocks. Among the mineral accompaniments of these, 

 w^e only noticed traces of iron, of manganese, sulphurets of iron, and native gold. 

 Other metallic ores, among which are silver and copper, are known on the Isthmus, 

 but their existence was not detected here. 



The region under present notice is traversed by broad parallel and conformable 

 dykes and belts of adhesive, unctuous, yellow clay. Within these dykes are imbedded 

 auriferous quartzose veins, of from one to three feet in thickness ; sometimes even 

 more. This quartz is made up of numerous threads and of smaller seams of shattered 

 materials. These consist of siliceous matter, frequently cellular, abounding in small, 

 well defined crystals, intermixed with iron pyrites. To the eye of the practical miner 

 they present very favorable appearances for an abundant amount of gold. From its 

 extremely broken condition in the mine, the quartz gangue is capable of beino" 

 crushed with the utmost facility, by the Chilian process. 



The form in which the metal is commonly obtained here, especially from the 

 washings and the surface operations, is of the kind commonly denominated " gold 

 dust;" that is to say, it prevails in grains and small foliated particles. Pieces of 

 half an ounce in weight have also been collected here. But the most novel and 

 interesting form in which the gold exists, is presented in beautiful fibres and delicate 

 threads of gold, which radiate from a large central mass of the same metal. 



As in most, perhaps in nearly all gold veins, the rich auriferous beds are 

 accompanied by others which are either of inferior value, or contain no gold 

 whatever. In the Palenque region, of which we now speak, it seems very probable 

 that an unusual number of veins contain the precious metal. 



