464 



NOTES ON BRAZIL. 



for the veins all tend to some larger one, and finally terminate in a 

 general mass, which now fills what appears to have been a passage or 

 chamber in the body of the mountain, and w^iich, according to the 

 language of Brazilian Miners, may be called the caldeirao or centre, or 

 perhaps nucleus of the quartz. These veins, I conceive to be the only 

 natural beds of Gold ; the matrix in which it is formed, though not 

 always enriched with metal, and in many respects answering to some- 

 what similar veins, in a different kind of mountains, where Lead is 

 discovered. 



The Serro of which we are speaking seems to be composed internally 

 of a soft kind of gneiss, which is remarkably full of narrow veins of 

 quartz, running through it in planes nearly perpendicular to the horizon. 

 In these alone, and in no other part of the mountain, the gold is found 

 in its matrix, running through the spar in small threads, or filling up 

 every interstice which it finds between the crystals so completely as to 

 appear like metal fused and poured into a mould, of which it takes the 

 exact form. From these and other appearances, therefore, I am inclined 

 to think, that Gold is produced by the action of water upon quartz 

 already existing, under some peculiar and yet unknown modifications. 

 If the metal had existed as a native and completely formed substance, 

 among the soft rudiments of the spar, which are sometimes, even at this 

 period, discovered, it would most likely have been detected there, which 

 I believe has never been the case ; and if the precious metallic particles, 

 by the hardening and crystalizing of these rudiments, have been thrown 

 into a more compact and tangible form, they must remain hidden in the 

 veins until these are themselves worn down, reduced, and broken. The 

 common Cascalho of the country which contains gold, seems indeed to 

 consist of the fragments of those veins which have been by some means 

 broken up, perhaps several ages ago, rolled about by the action of water 

 in agitation, and buried by it among the clays which have composed its 

 bed. These fragments and half rounded masses, it is evident, must have 

 contained the metal completely formed before the period of their disrup- 

 ture, however long it may have been since that event took place ; never- 



