1856.] ANSTED COBRE LODE. 153 



In passing along the railway from the harbour towards the mines, 

 the first thing seen is a bedded greenstone-porphyry, and as the 

 road tends to the north of west (intersecting the strike of the beds, 

 which dip northwards), we come successively on newer beds. These 

 include, first, shales and alternating beds of basalt, partly columnar 

 and partly in concentric blocks of various dimensions. To these 

 succeed bands of grit, and rotten altered rock, after which come in 

 nodular sandstones and greenish grits with calcareous lumps, di- 

 stinctly passing into greenstone and porphyritic conglomerate. This 

 is the general sequence ; but there is a special example near the 

 bifurcation of the Cobre lode, which is also deserving of notice. 



At this point the rock on the south side of the main lode and 

 contra lode, as seen in actual contact with the vein, of which it forms 

 the hanging-wall, is a fine-grained porphyry, compact and hard, and 

 of crystalline appearance. At the distance of a few yards, this por- 

 phyry is succeeded by, or passes into, a conglomerate, made up of 

 angular fragments, some of them of large size and of extremely 

 irregular composition. At no great distance, but still to the south, 

 and in a cutting close to the right bank of the Cobre river, a grit- 

 stone is seen, covered by conglomerate ; and a little further off, in 

 the direction of the branch, the porphyries altogether replace the 

 grits and conglomerates. 



Lastly, In a quarry close to the hanging wall of the great lode, 

 and near its richest part, the green porphyritic rock is quarried for 

 road material ; while close by, to the south, and near the branch, 

 the conglomerate takes its place. It is almost impossible to repre- 

 sent in a diagram the near approximation and complete intermixture 

 of the crystalhne rock with the bedded conglomerate, while the 

 chemical characteristics of the two are sufficiently similar to justify 

 the conclusion that one is only a modification of the other. 



There are few or no marks of direct igneous action, in the ordinary 

 sense of the term, with the exception of the bedded basalts, and 

 other rocks of this kind. 



Conclusion. — The Cobre lode is thus remarkable for its great mag- 

 nitude and comphcation, its extraordinary richness, the high degree 

 of mineralization of the surrounding " country," the nature of its en- 

 closing rock, and the combination of metamorphic and mechanically 

 formed rocks, in close contact, and frequent alternation. It possesses 

 the ordinary characteristics of veins only in some respects, and is 

 in others very anomalous. It is situated in a district not much re- 

 sembling in any point those in which copper is usually found, and 

 the general geology of the surrounding country would hardly indi- 

 cate so rich and remarkable a deposit as that which has been proved 

 to exist. The study both of the phenomena of the lode and of the 

 surrounding rocks, would well repay a longer time than I was able 

 to afford ; and I shall be happy if my remarks, by attracting atten- 

 tion, may serve to the further elucidation of the exceptional appear- 

 ances I have referred to. 



