Relations of Trap-Bocks with Ores of Copper. 301 



The characters of the gabbro, analogous to those of the 

 spilites, leave the mind in doubt as to their origin. "When 

 we observe them constituting insulated pitons, with forms 

 similar to those of the serpentine pitons, we are tempted to 

 suppose them eruptive ; but, on the other hand, they are con- 

 nected with slaty rocks evidently stratified {galestri and mat- 

 toni) ; and we cannot fail, moreover, to be struck with the 

 fact, that the condition of their existence is the contact of the 

 serpentine masses to which they are always subordinate. On 

 examining from a distance certain upraised masses, whose 

 sides have been laid bare, and keeping in view the move- 

 ment of the rocky masses, and their structure on a large scale, 

 the eye seizes, with considerable precision, what form the 

 lines of separation between elevating rocks and such as have 

 been elevated. Then, on approaching nearer, we perceive 

 that the lines of contact thus presented, always leave the 

 gabbro with the stratified rocks. 



The study of the green gabbro confirms this classification 

 of the gabbro-rosso among the rocks of contact. The serpen- 

 tine, indeed, presents physical characters contrasting so 

 strongly with the gabbro-rosso, that we feel difficulty in ad- 

 mitting that the latter rock is derived from the former ; the 

 green gabbro proves the transition. This rock, in fact, is 

 steatitic, like the serpentines to which it is sometimes united, 

 as well as to the slaty rocks evidently stratified. At the 

 same time, it likewise passes into the gabbro-rosso, by be- 

 coming streaked with the red sporadical parts, and then be- 

 ing generally charged with the peroxide of iron. It thus ap- 

 pears to us demonstrated, that the gabbro-rosso was nothing 

 more than a green gabbro of contact, which had been subjected 

 to particular influences, the result of which has been to charge 

 the rock with oligistic iron, rendering it everywhere harder 

 and more crystalline. 



The ores of copper and iron which form the characteristic 

 feature of the metalliferous chain, are either in some measure 

 enclosed in the rocks of contact, or disseminated through the 

 eruptive amphibolites which are themselves connected with 

 the serpentines. Thus the steatitic veins which, for the most 



