292 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



nodules, following the line of junction between the serpentine and 

 the gabbro rosso. Not that any distinct formation exists between 

 these two rocks ; but the copper ore itself generally lies between 

 them ; sometimes extending itself into the gabbro, and more fre- 

 quently into the serpentine, in which it forms large deposits, near 

 the junction of the two rocks. 



a. Gabbro rosso. 



b. Serpentine. 



c. Vein of Serpentine. 



When this mine was opened, a narrow vein of soft talcose ser- 

 pentine appeared on the surface, penetrating the gabbro rosso. 

 (See diagram.) This was followed down in a N. E. direction in 

 search of copper ; and at /the depth of 66 metres, the miners 

 found what appeared to be another vein rising up from the oppo- 

 site side, and forming a conjunction, as they call it ; and at this 

 spot a very rich deposit of ore was discovered. The main shaft has 

 been sunk so as to strike on this spot, which is, as it were, the apex 

 of a dome of serpentine, over which metallic deposits are found in 

 all directions, following the line of junction between the serpentine 

 and the overlying gabbro rosso. Below this junction point, 

 the shaft, to the depth of some hundred feet, passes through solid 

 serpentine only ; which, although soft at first, becomes so hard as 

 to require to be blasted with powder. The ore is a sulphuret (?). 

 The richest portions, which are of a blue-iron colour, produce 

 from 60 to 65 per cent., the poorest about 25 to 30 per cent. 

 The ore is generally in the form of irregular nodular masses, here 

 called ore stones, varying in size from a man's hand to masses 

 several feet in diameter. Sometimes it occurs in large deposits 

 several feet in length and height, and at others it forms a con- 

 tinuous band of a regular thickness, extending some distance 

 along the line of junction of the two rocks. Large masses have 

 also occasionally been met with in the cross galleries, at a distance 

 of 25 feet from the red gabbro, and, on one or two occasions, 

 nodular masses have even been found in the gabbro rosso itself 

 close to the serpentine, which must be considered as the principal 



